DE10313194A1 - Optical sensor for detecting objects e.g. for protecting personnel around machine tool, detects object if distance values lying within protection field are registered in all angle segments of resolution region - Google Patents

Abstract

The angular range of the monitored region is divided into a number of angle segments. For each segment, at least one distance value is derived from received light signals in an evaluation unit (8). At least one protection field is stored in the evaluation unit, and angle-dependent resolution regions are provided, the sizes of which are adapted to the width of a reference object arranged at the respective angular position at the edge of the protection field. The evaluation unit generates an object indication if distance values lying within the protection field are registered in all angle segments of at least one resolution region. An independent claim is included for a method of detecting objects using an optical sensor.

Description

The The invention relates to an optical sensor and a method for Detection of objects using an optical sensor.

Such an optical sensor is from the DE 19 917 509 C1 known. This optical sensor is used to detect objects in a monitoring area and has a distance sensor with a transmitter emitting light rays and a receiver receiving light rays. An evaluation unit is used to evaluate the received signals at the receiver. Furthermore, a deflection unit is provided, on which the transmitted light beams are deflected so that they periodically sweep over the monitoring area. The dimensions of various protective fields are stored in the evaluation unit. An arrangement of switches can be used to selectively select one of these protective fields, so that the objects within this protective field are detected.

at Such optical sensors are used for the current deflection positions the transmitted light rays the distances of an object to the optical one Sensor determined. Is for a distance measurement registers a distance value that is within the Protective field, the generation of a Object message. So that can Objects within the protective field quickly, i.e. with short response times can be detected.

such Optical sensors are used particularly in the area of personal protection used. For example, the apron is used with the optical sensor of an implement such as a machine tool or a press. About threats excluded from people becomes the implement deactivated by generating an object message, i.e. off. This ensures that a person who intervenes in the apron of the machine is not at risk is exposed.

in the Apron of such tools can depending on the machining processes that are carried out with the tools, small objects such as chips or small parts in the optical Monitored the sensor Penetrate area. The transmitted light beams hit such Small objects arranged within the protective field become these recognized as lying within the protective field, i.e. it will be one Object message generated, which leads to the shutdown of the implement, though no person or one to be protected Object has entered the protective field.

By such shutdowns becomes availability of the implement in an undesirable way reduced.

The The object of the invention is to provide an optical sensor, with which one if possible safe and interference-insensitive detection of objects becomes.

to solution this object, the features of claims 1 and g are provided. Advantageous embodiments and appropriate further training the invention are described in the subclaims.

The optical according to the invention Sensor has a distance sensor element with a transmitted light beam emitting transmitter and a receiving light beam receiver on. Furthermore, the optical sensor has a deflection unit, by means of which the transmission light beams periodically within a monitoring area defining angular range are on. In addition, an evaluation unit for evaluating the am Output of the recipient pending receive signals provided. The angular range is in divided a predetermined number of angle segments, each for Angle segment in the evaluation unit from the received signals in each case at least one distance value is derived. In the evaluation unit at least one protective field is stored. Furthermore, in the Evaluation unit depending on the angle resolution ranges given their sizes to the width one arranged in the respective angular position on the edge of the protective field Reference object are adjusted. Then only in the evaluation unit generates an object message if at least in all angular segments a resolution area distance values lying within the protective field are registered.

According to the method according to the invention the specification of the angle-dependent resolution ranges such that their size each corresponds to the section of the angular range over which a there Reference object of a given width arranged at the edge of the protective field extends.

The The basic idea of the invention is therefore that through the definition that refer to a given reference object at the edge of the protective field resolution ranges only objects with a specified minimum size are recorded.

The reference object preferably consists of a cylindrical body, the diameter of which is in relation to the typical dimensions of a human leg.

By this definition of the reference object is suitable for the optical device according to the invention Sensor especially for Calls in the field of personal protection. It is particularly suitable the optical according to the invention Sensor for Area monitoring applications on dangerous work equipment such as machine tools and presses. With the optical The sensor is then used to monitor the intrusion of people and objects into a protective field Dimensions are adapted to the danger area in front of the implement.

According to the invention an object message by the optical sensor that leads to a shutdown of the implement leads, only if for everyone within a resolution range lying angle segments lying within the protective field Distance value is determined.

The resolution ranges are angle-dependent defined, i.e. the sizes of the resolution ranges hang from the angular position at which the respective object is detected will start.

there is preferred for each angular segment the size of the resolution area individually specified. The definition of the resolution range for an angle segment takes place depending the position of the edge of the protective field in this angular range, the preferably as a distance limit in the evaluation unit of the optical Sensor is stored. From this distance limit and the specified width of the reference object is calculated in the evaluation unit via how many angular segments are arranged there at the edge of the protective field Reference object extends. The number of angle segments determined in this way corresponds to the size of the resolution area. This way, for the individual angle segments the sizes of the resolution ranges Are defined.

The resolution ranges determined in this way the smaller the bigger the Distance limit for that respective angle segment is. Which leads to an angle-dependent, definition of the resolution areas depending on the respective position of the protective field edge and thus the minimum sizes of objects, their entry leads to an object message.

Becomes an object in a section of the one swept by the transmitted light beams Angle range detected in which a large representative of the protective field edge Distance limit is present, the resolution range is correspondingly small. This means that the number of angular segments falling within the resolution range is correspondingly small. This in turn means that in this one small number of object detections in these angular segments is sufficient, to generate an object message.

Accordingly is in angular segments of the surveillance area, in which small values for the distance limit values are available, the resolution range is correspondingly larger. Accordingly, there must be within a large Number of successive angular segments that cover the respective resolution range form, object interventions in the protective field are registered in order trigger an object message.

By this angle dependent Allocation of the resolution areas is guaranteed on the one hand that everywhere in the protective field, objects whose widths are greater than or equal to the width of the reference object are securely recorded.

Farther is due to the angle Specification of the resolution areas guaranteed that these resolution areas dependent have the smallest possible expansion from the position of the protective field edge around safety-critical objects whose widths are larger or are the same as the reference object.

Thereby it is achieved that small particles arranged in the protective field do not to an unnecessary generation an object message and thus lead to an unnecessary shutdown of the implement.

Consequently is with the optical according to the invention Sensor one alike safe and insensitive to interference Object detection guaranteed.

The Invention is explained below with reference to the drawings. It demonstrate:

1 : Schematic representation of an embodiment of the optical sensor.

2 : Schematic representation of a by means of the optical sensor according to 1 monitored protective field.

3 : Detailed representation of the protective field according to 2 with a resolution range.

4 : Schematic representation of object detection using the optical sensor in the protective field according to 3 ,

1 shows an embodiment of an optical sensor 1 for detecting objects. The optical sensor 1 has a distance sensor ment with a transmitted light beam 2 emitting transmitter 3 and a received light beam 4 receiving recipient 5 on. The transmitter 3 consists preferably of a laser diode, which is used for beam shaping of the transmitted light beams 2 a transmission optics 6 is subordinate. The recipient 5 is formed for example by a photodiode, which has a receiving optics 7 is upstream.

The distance measurement can take place on the one hand according to the principle of phase measurement. In this case, the laser diode is operated in the CW range, with the transmitted light beams 2 amplitude modulation is applied. The distance information is received at the receiving end by comparing the phase positions of the emitted transmitted light beams 2 and the one reflected back from an object and onto the receiver 5 incoming light beams 4 determined.

This evaluation takes place in an evaluation unit 8th to which the broadcaster 3 and the recipient 5 are connected via supply lines, not shown. The evaluation unit 8th is formed in the present embodiment by a microcontroller.

Alternatively, the distance measurement can also be carried out using the pulse transit time method. In this case, the transmitter 3 short transmitted light pulses emitted. In this case, the distance information becomes an object and back to the receiver by direct measurement of the transit time of a transmitted light pulse 5 won.

The broadcast 2 and received light beams 4 are via a deflection unit 9 guided. The deflection unit 9 has a deflecting mirror 10 on which on a rotatable, via a motor 11 powered pedestal 12 seated. The deflecting mirror 10 thereby rotates at a predetermined speed around a vertical axis of rotation D. In the present case, the deflecting mirror rotates 10 at a constant speed. The transmitter 3 and the recipient 5 are in the axis of rotation D above the deflection mirror 10 arranged.

The deflecting mirror 10 is inclined by 45 ° with respect to the axis of rotation D, so that it is on the deflecting mirror 10 reflected transmitted light rays 2 running in the horizontal direction from the optical sensor 1 are led. The transmitted light rays penetrate 2 an exit window 13 which is in the front wall of the housing 14 the device 1 is arranged. The housing 14 is essentially cylindrical, with the exit window 13 extends over an angular range of 180 °. Accordingly, how in particular 2 can be seen with the transmitted light beams 2 a semicircular flat surface is scanned covering a surveillance area 15 forms within which objects are detectable. The surveillance area 15 is limited by the maximum distance that can be detected by means of the distance sensor element. The received light rays reflected back from the objects 4 enforce the exit window in a horizontal direction 13 and are above the deflecting mirror 10 to the recipient 5 guided.

In order to record the positions of the objects, the evaluation unit is used by means of a not shown 8th connected angle encoder continuously the current angular position of the deflection unit 9 detected. The angular position and the distance value registered in this angular position become in the evaluation unit 8th determines the position of an object.

Such optical sensors 1 are also used in particular in the field of personal protection, the evaluation unit being used to meet the safety requirements 8th has a redundant structure.

In such security-related applications, the detection of objects and people typically does not take place within the total of the transmitted light beams 2 swept area, but within a limited protective field 16 , An example of such a surveillance area 15 is in 2 shown. In this case, the protective field 16 formed by a rectangular flat surface. Once an object or person is in this protective field 16 penetrates, there is an object message. This object message can be used, for example, to switch off a machine, its apron by means of the optical sensor 1 is monitored, used.

The dimensions of the protective field 16 are in the evaluation unit 8th saved as parameter values. Here is the protective field 16 clearly defined by its edge contour, which can be specified in a teach-in process or as a predefined parameter set in the evaluation unit 8th is readable.

How out 2 the monitoring area can be seen 15 over an angular range of 180 °. The positioning of objects in the surveillance area 15 takes place in that for predetermined angular positions of the deflection unit 9 and thus the transmitted light rays 2 the distance of an object to the optical sensor 1 is determined. The distance is determined depending on the angular positions not continuously but with a limited angular resolution that is essentially predetermined by the respective measuring times. Accordingly, the surveillance area is 15 forming angular range as in 3 shown divided into discrete angle segments w _{i of the} same size. According to this division, too Edge contour of the protective field 16 defined as a discrete traverse over the angle segments w _i . A distance limit value D _{i is} assigned to each angle segment w _i . How out 3 can be seen, a distance limit value D _{i is} assigned to the beginning of an angle segment w _i in the present case. The edge contour of the protective field is in the form of this map 16 in the evaluation unit 8th stored.

For detection in the protective field 16 intruding people or objects are during the operation of the optical sensor 1 the current in the angular segments w _i currently determined distance values d _i with the respective edge of the protective field defining distance limit values D _i are compared. In the present case, a distance value d _{i is} determined only at the beginning of an angle segment w _i . In the event of an intervention in the protective field 16 is in the corresponding angular segment w d _{i i} a registered below the distance limit value D _i lying current distance value.

In principle, could be in the evaluation unit 8th an object message can already be generated if the transmitted light beams occur during a scanning period 2 an object intrusion is registered in an angular segment w _i .

To avoid unnecessary object reports and the associated shutdowns of the machine, its apron with the optical sensor 1 is monitored, is in the evaluation unit 8th generates an object message only when detecting objects or people with a specified minimum size.

For use in the field of personal protection, it is necessary to maintain the required level of security with the optical sensor 1 a cylindrical body with a given diameter and a defined surface condition within the entire protective field 16 is captured safely.

To meet this requirement, the data of the body, in particular its diameter, are used as the reference object in the evaluation unit 8th of the optical sensor 1 stored. The reference object defined in this way is used in the evaluation unit 8th for the definition of resolution areas A _i depending on the edge contour of the protective field 16 used.

The specification of the resolution areas A _i is in 3 illustrated. A resolution range A _i is advantageously defined for each angle segment w _{i as} a function of the associated distance limit value D _i , which corresponds to the position of the protective field edge in this angle segment w _i .

From the distance limit D; an angle segment w _i and the known diameter of the reference object is in the evaluation unit 8th calculates the number of angle segments over which a reference object lying in this angle segment w _i at the protective field edge would extend. The number of the angular segments covered by the reference object defines the size of the resolution area A _i . At the in 3 In the exemplary embodiment shown, the resolution range A _i assigned to the angle segment w _i comprises three angle segments w _i . Here, in the present case the angular segment w _i associated resolution area _A is defined such that it in the scanning direction S of the transmitted light beams 2 the angle segments w _i , w _{i + 1} , w _{i + 2} and thus the distance values d _i , d _{i + 1} , d _{i + 2} falling in these angle segments or the distance limit values D _i , D _{i + 1 assigned to them} , D _{i + 2} includes. However, other positions of the resolution range A _i relative to the angular segment w _{i are also} possible. This in 3 The illustrated embodiment is not to scale and is only used to illustrate the definition of the resolution areas A _i . The angle segments w _i are typically adapted to the resolution of the distance measurement. With a diameter of the reference object of typically 70 mm, a resolution range A _i therefore includes a corresponding number of angle segments w _i with protective field limit values in the range of a few meters.

Each resolution area A _i advantageously consists of an integer number of angle segments w _i , w _{i + 1} , ....

As in 4 for object detection, the distance values d registered in the individual angle segments w _i , w _{i + 1} , ... of a resolution range A _i are illustrated; evaluated. It is in the evaluation unit 8th then an object message, which leads to the machine being switched off, is generated when the respectively registered current distance value d _{i is} below the distance limit value D _i in all angle segments w _{i of} a resolution range A _i .

In this way it is achieved that objects whose sizes are greater than or equal to the size of the reference object at any location in the protective field 16 is safely defined. At the same time, object messages are suppressed when objects that are smaller than the reference object are detected, so that protective field violations caused by interference do not result in the machine being switched off, which increases its availability.

The maximum sizes of the objects for which an object message is suppressed depend on their positions in the protective field 16 and in particular depending on the position of the protective field edge.

This is based on the in 4 schematically illustrated detection of an object G and a second object G 'illustrated. The objects G, G 'have the same width, which is also smaller than the width of the reference object. Objects G, G 'are therefore not safety-critical objects, the detection of which should not lead to the generation of an object message.

How out 4 can be seen in the scanning direction S of the transmitted light beams 2 the object G is first detected in the angular segment w _i during a scanning period. According to the distance limit D; a resolution range A _{i is} assigned to this angle segment w _i . The object G is smaller than the reference object. However, since this object G lies far ahead of the protective field boundary, the object G is detected in all three angle segments w _i , w _{i + 1} , w _{i + 2,} which belong to the resolution range A _i , ie in all three angle segments w _i , w _{i + 1} , w _{i + 2} , the current distance values d _i , d _{i + 1} , d _{i + 2} registered there lie below the distance limit values D _i , D _{i + 1} , D _{i + 2.} Therefore, when the object is detected, G in the evaluation unit 8th generates an object message.

In contrast, the Detection of object G 'is not to an object message, although this is the same width as the object G.

How out 4 the object G 'can be seen in front of the lateral area of the protective field edge, which is much closer to the optical sensor 1 lies like the front edge of the protective field edge.

Therefore, the resolution range A _j , which is defined on the basis of the angle segment w _j in which the object G 'is detected for the first time, comprises a larger number of angle segments w _j , w _{j + 1} , ... than the resolution range A _j ,

This is due to the fact that the angular segment w _j is associated with a distance limit value D _j, which is considerably smaller than that of the angular segment w _i associated with distance-limit value D _i. Accordingly, the resolution range A _j comprises a larger number of angle segments w _i , w _{i + 1} , ... than the resolution range A _i . In the present example, which is again not to scale, the resolution range A _i comprises five angle segments w _j , w _{j + 1} , ..., w _{j + 4,} while the resolution range A _i only comprises three angle segments w _i , w _{i + 1} , w _{i + 2} includes.

How out 4 the object G 'can be seen relatively close to the protective field boundary. Accordingly, the object G 'is not detected in all angle segments of the resolution area A _j . The detection of the object G 'therefore does not lead to an object message.

(1)

optical sensor

(2)

Transmitted light beams

(3)

Channel

(4)

Receiving light rays

(5)

receiver

(6)

transmission optics

(7)

receiving optics

(8th)

evaluation

(9)

Deflector

(10)

deflecting

(11)

engine

(12)

base

(13)

exit window

(14)

casing

(15)

monitoring area

(16)

protection field

Claims (11)

Optical sensor with a distance sensor element consisting of a transmitter emitting transmitted light rays and a receiver receiving received light rays, with a deflection unit by means of which the transmitted light rays are guided periodically within an angular range defining a monitoring range, and with an evaluation unit for evaluating the received signals at the output of the receiver, thereby characterized in that the angular range is divided into a predetermined number of angular segments, wherein for each angular segment in the evaluation unit ( 8th ) at least one distance value is derived from the received signals, that in the evaluation unit ( 8th ) at least one protective field ( 16 ) is stored in the evaluation unit ( 8th ) angle-dependent resolution ranges are specified, the sizes of which correspond to the width of one in the respective angular position at the edge of the protective field ( 16 ) arranged reference object are adapted, and that in the evaluation unit ( 8th ) an object message is only generated if in all angle segments of at least one resolution area within the protective field ( 16 ) lying distance values are registered. Optical sensor according to claim 1, characterized in that the deflection unit ( 9 ) a deflecting mirror rotating around an axis of rotation ( 10 ) having. Optical sensor according to claim 2, characterized in that it has an angle sensor for detecting the current angular positions of the deflecting mirror ( 10 ) having. Optical sensor according to one of claims 2 or 3, characterized in that the deflecting mirror ( 10 ) rotates at a constant speed. Optical sensor according to one of claims 1-4, characterized characterized in that the angular range is the same in angular segments Size divided is. Optical sensor according to one of Claims 1-5, characterized in that each angular segment has an edge of the protective field ( 16 ) is assigned a corresponding distance limit value with which the current distance value determined in the angle segment is compared. Optical sensor according to one of claims 1-6, characterized characterized that every resolution area includes an integer number of angular segments. Method for detecting objects by means of an optical sensor according to one of claims 1-7, comprising the following method steps: determination of distances of objects by means of a distance sensor element, consisting of a transmission light beam ( 2 ) emitting transmitter ( 3 ) and a received light beam ( 4 ) receiving recipient ( 5 ), depending on the angular positions of a deflection unit ( 9 ), by means of which the transmitted light beams ( 2 ) periodically within a monitoring area ( 15 ) defining the angular range, dividing the angular range into a predetermined number of angular segments, with an evaluation unit ( 8th ) for each angle segment from the received signals at the output of the receiver ( 5 ) at least one distance value is derived in each case, specification of one within the monitoring area ( 15 ) protective field ( 16 ), Specification of angle-dependent resolution ranges, each of which corresponds to the section of the angle range over which there is an edge of the protective field ( 16 ) arranged reference object of a given width, generation of an object message if, in all angular segments, at least one resolution area within the protective field ( 16 ) lying distance values are registered. A method according to claim 8, characterized in that the edge of the protective field ( 16 ) in the form of a map in the evaluation unit ( 8th ) is saved in which each angular segment of the angular range has an edge of the protective field ( 16 ) corresponding distance limit is assigned. A method according to claim 9, characterized in that depending on the angular segments the distance limits resolution ranges be assigned. A method according to claim 10, characterized in that in the evaluation unit ( 8th ) for an angle segment the size of a resolution range is calculated from the fact that the number of angle segments is calculated from the distance limit value assigned to this angle element and the width of the reference object, over which the distance to the optical sensor corresponding to the distance limit value is calculated ( 1 ) arranged reference object extends.