DE19544632A1 - Opto-electronic system for detecting objects in surveillance area e.g. of textile production - Google Patents

Abstract

The system has a receiver and beam transmitters located at the edges of the surveillance area and, if the beam path between them, is interrupted an alarm is given. The receiver (3) consists of a linear arrangement of photo sensitive cells (6) illuminated by light beams (5) and the positions of the cells and the beam transmitters (4) are stored in an evaluation unit (8). During a calibration phase the evaluator records whether the cells are illuminated or not and stores this data as reference data. During the subsequent in-service phase these data are continually compared with the actual status of the cells. The shaded areas detected by the receiver, caused by interruption of the light beam, are recorded in the evaluation unit in respect of size and number, based on comparison of the reference data and the actual status data, and can initiate an alarm. In combination with the positions of the light beam transmitter and receiver this provides a measure of the size and position of the interrupting object (2) in the surveillance area.

Description

The invention relates to a device according to the preamble of the An saying 1.

Devices of this type are used, in particular, for thread breakage control at Tex til machines or used for drill break control in machine tools.

The optoelectronic device is designed as a light barrier. The transmitter consists preferably of a light emitting diode, the receiver of a photodio de. The transmitter and the receiver are arranged opposite one another so that If the beam path is clear, the transmitted light beams emitted by the transmitter meet the recipient. Is an object, for example a thread or a boh rer, arranged in the beam path, the beam path is at least partially interrupted, so that a smaller amount of light from the transmitted light beam hits the recipient.

The transmitted light striking the receiver is converted into a voltage signal converts which by means of a threshold value generating threshold value is assessed.

With a free beam path, a large amount of light hits the receiver, see above that the voltage signal is above the threshold. Correspondingly lies the voltage signal below the threshold as soon as an object is shining gear is arranged.

In this way, in the surveillance area between transmitter and emp objects arranged in a catcher are recognized.

The disadvantage here, however, is that this device only recognizes who can, whether a beam has been interrupted by an object or Not. However, no information is received about which Be  is the object, especially what size and geometry the object ject. Furthermore, no statements can be made about where in the Monitoring area the object is arranged. Finally, by means of a such device can not be distinguished whether an object or several objects are in the beam path.

The invention has for its object a device of the beginning ge named type so that the size, geometry, position and number can be determined by objects in the surveillance area.

The features of claim 1 are provided to achieve this object. Advantageous embodiments and expedient further developments of the Erfin tion are described in claims 2-7.

According to the invention, the receiver consists of a linear arrangement of photosensitive elements that face at least one transmitter. At A certain number of photosensitive elements become free beam path exposed by the transmitted light beams emitted by the transmitter.

The number of exposed elements depends on the beam characteristics of the Sen and the expansion of the photosensitive elements and their position on the right relative to the broadcaster.

An object occurs in the surveillance limited by the sender and receiver area, at least part of the transmitted light is shaded from the object tet and no longer reaches the recipient, so that in contrast to the free Beam path some photosensitive elements can no longer be exposed.

In an evaluation unit, those with a free beam path and with an im Objects located in the beam path exposed and unexposed photosensiti ven elements registered and compared.  

As a result, the part of the receiver surface shaded by the object becomes he averages. Both the sizes and the number of shadows are shaded th areas determined and output as object reports. In this way can determine the number of objects in the surveillance area will.

Because the positions of the recipient and the sender are also in the evaluation unit are saved, conclusions can be drawn from the shaded area who is drawn about the size and position of the object in the surveillance area the. For example, the contour can be obtained from the size of the shaded area of the object, if its position in the surveillance area is known. Conversely, the position of the object in the surveillance area be determined if its contour and orientation in the surveillance area is well known.

In a particularly advantageous embodiment, two transmitters are along one straight lines parallel to the longitudinal axis of the receiver in front of the emp arranged catcher, the transmitters are activated alternately.

The objects in the surveillance area are therefore under from the transmitters hit different angles and thus produce very different ab shading pattern in the receiver. From the shading patterns and the posi tion of the transmitter can evaluate the size and position of an object unit can be calculated.

Another advantage of the device according to the invention is that time Object properties that can change, such as position and size can be easily registered and evaluated.

For example, the temporal change in the thread thickness during the passage be detected by a textile machine. The company led by the machine which penetrates the monitoring area axially and is continuously  Device detected. If the thickness of the thread varies, the shading changes pattern on the receiver. In this way, changes in the The thickness of threads or comparable objects can be detected quickly and safely will.

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

Fig. 1 is a block diagram of the optoelectronic device.

Fig. 2 Schematic representation of the optoelectronic device with a receiver and a transmitter and an object arranged in the surveillance area.

Fig. 3 Schematic representation of the optoelectronic device according to FIG. 2 with two objects arranged in the monitoring area.

Fig. 4 Schematic representation of the optoelectronic device with a receiver and two transmitters and an object arranged in the surveillance area.

FIG. 1 shows an optoelectronic device 1 for detecting objects 2 , which are shown in FIGS. 2-4, in a monitoring area. In the exemplary embodiment according to FIG. 1, the device 1 has an receiver 3 and two transmitters 4 . Alternatively, the device 1 can also have a transmitter 4 , as can be seen in particular from FIGS. 2 and 3.

The one or more transmitters 4 and the receiver 3 are arranged on opposite edges of the surveillance area so that the emitted by the transmitter 4 and directed towards the receiver 3 transmit light beams 5 are at least partially interrupted when an object 2 is arranged in the rich area .

The transmitter 4 consists for example of a light emitting diode. To focus the transmitted light, the transmitter 4 is preferably followed by a transmitting optic formed by a lens.

The receiver 4 consists of a linear arrangement of photosensitive elements 6 . The receiver 4 is preferably formed by a CCD line sensor. Such a CCD line sensor has up to 6000 individual photosensitive elements 6 arranged next to one another. Due to the large number of photosensitive elements 6 in a CCD line sensor, the objects 2 in the surveillance area can be detected with a high spatial resolution.

The receiver 3 is preferably preceded by an optical receiving system for focusing the incident light. Advantageously, the receiving optics consists of a rod lens, the dimensions of which are adapted to the dimensions of the photosensitive elements 6 .

The transmitted light impinging on the photosensitive elements 6 generates in the individual photosensitive elements 6 an analog received signal which, depending on the quantity of transmitted light impinging on it, corresponds to different grayscale levels.

The analog received signal is fed to an analog / digital converter 7 . There, the analog received signal is digitized using a threshold value. The threshold value is generated by a threshold value unit, which is preferably formed by a Schmitt trigger.

If the received signal of a photosensitive element 6 is above the threshold value, then this element 6 is exposed. If the received signal is below half the threshold value, the photosensitive element 6 is not exposed.

These digitized signal values are read into an evaluation unit 8 formed by a microcontroller. The signal values of the individual photosensitive elements 6 are read in serially. The reading cycle is specified and controlled by a CCD control unit 9 connected to the microcontroller and to the CCD line sensor. Typically, the signal values of the receiver can be read into the evaluation unit 8 up to 5000 times per second. As a result, objects 2 can be detected very quickly in the monitoring area.

The levels of the threshold values are advantageously adjustable via the evaluation unit 8 . In this way, the sensitivity of the receiver 3 can be varied.

At least one transmitter 4 is connected to the evaluation unit 8 and is formed, for example, by a light-emitting diode.

The diameter of the transmitted light beam 5 emitted by the transmitter 4 and the distance between the transmitter 4 and the receiver 3 is dimensioned such that as large a part of the emitted transmitted light as possible reaches the receiver 4 . The receiver 4 is advantageously completely illuminated by the transmitted light bundles 5 .

In the embodiment shown in Fig. 1, two transmitters 4 are easily seen, which are expediently designed identically. In order to achieve a clear separation of the transmitted light beams 5 striking the receiver 4 , the transmitters 4 are activated alternately via the evaluation unit 8 .

The frequency at which the two transmitters 4 are activated one after the other is so large that the position of an object 2 in the monitoring area remains unchanged when the activated transmitter 4 changes.

An input unit 10 and an output unit 11 are connected to the microcontroller. Via the input unit 10 , for example, the sensitivities of the individual photosensitive elements 6 can be specified by specifying a certain threshold value in the analog / digital converter 7 . In particular, object reports are output via the output unit 11 . The input and output of the data can be done in an analog as well as digital way.

The mode of operation of the device 1 according to the invention can be seen in particular from FIGS. 2-4.

In the embodiment shown in FIGS. 2 and 3, a Sen 4 is provided, which is arranged at a predetermined distance from the receiver 3 .

The transmitted light beams 5 emitted by the transmitter 4 illuminate most of the receiver 3 when the beam path is clear. The area swept by the transmitted light beams 5 between transmitter 4 and receiver 3 defines the monitoring area.

When the beam path is clear, the transmitted light beams 5 hit a certain number of photosensitive elements 6 , which are thereby exposed. The remaining photosensitive elements 6 remain unexposed. This pattern of the exposed and unexposed photosensitive elements is registered in the evaluation unit 8 . These signal values of the photosensitive elements 6 are stored as reference values during an adjustment phase in the evaluation unit 8 .

In a subsequent work phase, the monitoring area is monitored by continuously reading the signal values of the photosensitive elements 6 into the evaluation unit 8 , registering them as actual values and comparing them with the reference values.

If an object 2 enters the beam path of the transmitter 4 , part of the light beam 5 must strike the object 2 . Is the object, as shown in Fig. 2 Darge illustrated embodiment, opaque, so there is a full local shadowing on the receiver 3 , which depends on the size of the object 2 and its position in the surveillance area.

In Fig. 2, the edge rays emitted by the transmitter 4 , which affect the object 2 and hit the receiver 3 , are marked with the reference number R. These marginal rays define the edges of the area shaded by the object 2 on the receiver 3 . The part of the monitoring area shaded by the object 2 is highlighted in FIG. 2.

If object 2 is partially translucent, the shadowing of the transmitted light by object 2 is incomplete. Then, in the area of the shadowing, part of the transmitted light hits the receiver 3 . A corresponding choice of the threshold value in the analog / digital converter 7 can be used to differentiate between the transmitted light incident on the receiver 3 and the transmitted light which penetrates the object 2 . In this case too, the shadowing on the receiver 3 can be determined by the object 2 .

The transmission beam diameter is expediently considerably larger than the diameter of the objects 2 to be detected. Then the complete object contour is detected by the shadowing caused by object 2 .

In this case, the device 1 can be used particularly easily for counting objects 2 in the monitoring area. This is illustrated in FIGS. 2 and 3. In Fig. 2, a thread is shown which penetrates the surveillance area in the axial direction, while in Fig. 3 two parallel threads are spaced from each other.

Since the transmitter 4 and the receiver 3 are arranged so that the threads are not arranged one behind the other in the direction of the transmitted light beam axis, the threads produce two separate shading areas on the receiver 3 , which are registered and evaluated in the evaluation unit 8 . The output unit 11 can then be used, for example, to report that two objects 2 are arranged in the monitoring area.

The device 1 shown in FIGS. 2 and 3 can also be used advantageously for determining the relative size of objects 2 . Depending on the thickness of the thread, a certain size of the area shaded on the receiver 3 results.

If, for example, the thread is transported in a textile machine perpendicular to the monitoring area located in the plane of the drawing, device 1 can be used during the transport process to check whether the shaded area remains constant, ie the thickness of the thread remains unchanged. In this way, the quality of threads can be easily checked.

In addition, the thickness of the thread can be determined if its position in the monitoring area and the thickness of the thread are known. From the size of the shaded receiver area and the positions of the transmitter 4 and the receiver 3 , which are stored in the evaluation unit 8 , the geometric course of the marginal rays R can be calculated, from which the position of the thread in the monitoring area can be determined with a known thread thickness.

In FIG. 4 a device is shown with a receiver 3 and two transmitters 4. The transmitters 4 are arranged along a straight line parallel to the longitudinal axis of the receiver 3 Emp.

The beam characteristic of the individual transmitters 4 is selected in accordance with the arrangement shown in FIG. 2, so that the transmitters 4 illuminate almost the entire surface of the receiver 3 .

In this case, the monitoring area is formed by the area between the transmitters 4 and the receiver 3 , which is swept by the transmit light beam 5 from both transmitters 4 .

The object 2 located in the surveillance area is successively detected by the transmitted light beams 5 of the two transmitters 4 . Due to the different positions of the transmitter 4 , which, like the position of the receiver 3 , are stored in the evaluation unit 8 , the object 2 generates four shading patterns on the receiver 3 when the two transmitters are activated.

The size of the shading pattern is in turn determined by comparing the actual values with the reference values. Since two transmitters 4 are seen in this case, which are activated one after the other, 4 individual reference values, which are determined during the adjustment phase, are stored for each transmitter. Depending on which transmitter 4 is activated, the actual values, which are determined with one of the transmitters 4 , are compared with the reference values of the corresponding transmitter 4 .

Two different shading patterns are thus determined for an object. From the shading patterns and the positions of the transmitter 4 and the receiver 7 , the course of the marginal rays R₁, R₂ of the transmitted light beam 5 , which are guided past the edges of the object 2 on the receivers 3 , can be determined. These edge rays R₁, R₂ each define the edges of the shading areas on the receivers 3 .

The geometric course of an edge ray R₁ or R₂ corresponds to a Gera that runs between the edge of a shading area and one of the transmitters 4 . For each shading area there is, if an object 2 is arranged in the surveillance area, two of these edge rays R₁ or R₂ for both transmitters together, thus four edge rays R₁ and R₂.

The contour and the position of the object 2 in the monitoring area in the evaluation unit 8 are determined by calculating the intersections S 1, S 2 of two edge beams R 1 and R 2 of different transmitters 4 .

The edge rays R₁, R₂, which originate from the inner edges of the shading zones, are cut together and form the first intersection S₁. The two remaining, outer edge rays R₁, R₂ are used to determine the second intersection S₂ ( Fig. 4). The distance between the intersections S₁ and S₂ gives the size of the contour of the object 2 and its position.

For this intersection calculation, two sets of signal values, which are generated in succession by the various transmitters 4 , are evaluated together.

Since the repetition frequency with which the transmitters 4 are activated is so great that the position of the object 2 in the surveillance area remains unchanged during the successive activation of the two transmitters 4 , arises from the intersection of edge rays R 1, R 2, which follow one another in time were determined, no error in the position and contour determination of object 2 .

In the embodiment shown in FIG. 4, the object message expediently consists in the output of the size and position of the object 2 in the monitoring area. In addition, this arrangement, like the arrangement shown in FIGS. 2 and 3, can be used for counting objects 2 in the monitoring area.

Claims (7)

1. Optoelectronic device for detecting objects in a monitoring area with a receiver and at least one sensor, which are arranged opposite one another at the edges of the monitoring area in such a way that an object arranged in the monitoring area at least partially interrupts the beam path of the transmitted light from the transmitter to the receiver , whereupon an object message is triggered in an evaluation unit connected to the receiver, characterized in that the receiver ( 3 ) consists of a linear arrangement of photosensitive elements ( 6 ) which are exposed by the incident light beams ( 5 ) that in the evaluation unit ( 8 ) the positions of the photosensitive elements ( 6 ) and the transmitter ( 4 ) are stored in such a way that during an adjustment phase the photosensitive elements ( 6 ) exposed and unexposed in the free beam path are registered in the evaluation unit ( 8 ) and nd these signal values are stored as reference values, that during a working phase following the adjustment phase, the signal values of the photosensitive elements ( 6 ) are continuously registered and compared as actual values with the reference values and that by comparing the actual values with the reference values based on the Receiver ( 3 ) shaded areas, which che result from the object-related interruptions of the transmitted light beam ( 5 ), in terms of number and size, which in conjunction with the positions of the transmitter ( 4 ) and the receiver ( 3 ) is a measure of the size and Represent the position of the object ( 2 ) in the monitoring area, are detected in the evaluation unit ( 8 ) and can be output as an object message. 2. Device according to claim 1, characterized in that the receiver ( 3 ) is formed by a CCD line sensor. 3. Apparatus according to claim 1 or 2, characterized in that the distance from the sensor ( 4 ) to the receiver ( 3 ) and the length of the receiver are dimensioned such that the entire receiver ( 3 ) of the transmitted light beams ( 5 ) is illuminated. 4. Device according to one of claims 1-3, characterized in that the object diameter ( 2 ) is smaller than the diameter of the transmitted light beam ( 5 ). 5. Device according to one of claims 1-4, characterized in that two transmitters ( 4 ), which are alternately activated by the evaluation unit ( 8 ), on a straight line parallel to the longitudinal axis of the receiver ( 3 ) in front of the receiver ( 3 ) are arranged. 6. The device according to claim 5, characterized in that the transmitters ( 4 ) are identical. 7. Apparatus according to claim 5 or 6, characterized in that when each transmitter ( 4 ) is activated, the areas shaded by the objects ( 2 ) on the receiver ( 3 ) are determined from the positions stored in the evaluation unit ( 8 ) of the transmitter ( 4 ) and the receiver ( 3 ) and the shaded areas of the spatial profile of the objects ( 2 ) tangent and on the receiver ( 3 ) incident edge rays (R₁, R₂) of the transmitted light beam ( 5 ) is determined and by cutting the edge rays (R₁, R₂) the positions and contours of the objects ( 2 ) are calculated.