DE202012007402U1 - Optoelectronic sensor - Google Patents

Abstract

An optoelectronic sensor (11) for detecting objects in a surveillance area with an elongated housing (25) having a front light passage area (D) and defining a main sensor direction (S) through its longitudinal axis (L), a transmitter (13) emitting transmit light beams, a receiving light beam receiving receiver (14), wherein the transmitter (13) and the receiver (14) are arranged in the housing (25) such that their optical axes (OA1, OA2) respectively by at most 20 °, preferably by at most 10 ° deviate from the main sensor direction (S), wherein the optical axes (OA1, OA2) are defined as the spatial directions in which the light propagation of the transmitted light beams or the received light beams with maximum intensity, and a deflection module provided on the light passage surface (D) ( 29), which has a first deflection optics (37) for deflecting the transmitted light beam passing through the light passage surface (D) and a second deflecting optics (39, 43) acting separately from the first deflecting optics (37) for deflecting received light beams impinging on the deflecting module (29), the deflecting module (29) tilting the propagating directions of the transmitted light beams and the receiving light beams outside the housing (25) defined monitoring direction (Ü) relative to the main sensor direction (S) by a deflection angle (W) of not equal 0 ° and preferably 90 °, characterized in that at least one of the deflection optics, a prism (37, 39) with an interface (55a, 55b) whose surface normal has an inclination angle to the main sensor direction (S), which is half the deflection angle (W).

Description

The invention relates to an optoelectronic sensor for detecting objects in a surveillance area, comprising an elongated housing having a front light passage surface and defined by its longitudinal axis a main sensor direction, a transmitting light beam emitting transmitter, a receiving light beam receiving receiver, wherein the transmitter and the receiver in such the housing are arranged such that their optical axes each deviate by at most 20 °, preferably by at most 10 ° from the main sensor direction, and a deflecting module provided on the light passage surface, which has a first deflection optics for deflecting transmitted light rays passing through the light passage surface and one of the first deflection optics separately acting second deflection optics for deflecting received light beams which impinge on the deflection module, wherein the deflection module is a tilting of the propagation directions of the transmitted light beams and the receiving light beams outside the housing defined monitoring direction relative to the main sensor direction by a deflection angle of not equal to 0 ° and preferably 90 ° causes.

Such optoelectronic sensors are used for example in round light barriers, reflection light barriers, through-beam sensors or light sensors. The term "light passage area" is used here for a surface which is transversely - generally perpendicular - to the "viewing direction" of the transmitter and the receiver, on a side of the housing facing the area to be monitored, which is not necessarily to be understood objectively. The light passage area is defined by a front opening of the housing or by a front window closing this.

The term "optical axes" is used here for those spatial directions in which the light propagation of the transmitted light beams or of the received light beams takes place with maximum intensity.

The deflection module allows a so-called "radial light emission", that is, a light exit transverse to the main sensor direction. In contrast, one speaks of an "axial light emission" when the transmitted light beams undeflected the sensor housing, d. H. essentially straight along the main sensor direction, left. A radial light emission may be necessary in certain applications due to the spatial conditions. For example, the optical axes of the transmitter and the receiver are arranged in many cases parallel to the longitudinal axis of the housing so as to provide sufficient space for the optical components required for beam shaping. If at the installation of the space available behind the light exit point space is too small to accommodate the elongated sensor housing, can be created by using a sensor with radial light leakage remedy.

The invention also relates to so-called "V-keys" in which the optical axes of the transmitter and the receiver are arranged only approximately parallel to the longitudinal axis of the housing. Specifically, in such V-keys, the optical axes of the transmitter and the receiver are at an angle between 0 ° and 20 ° to each other and therefore intersect at a certain point in front of the housing. This is for defining a workspace.

Another problem with optoelectronic sensors of the type mentioned is that the adjustment of the scanning distance by means of a suitable potentiometer is usually to take place on the light exit opposite side of the housing. This is difficult to achieve for sensors with axial light emission.

In the in the DE 103 08 085 B4 disclosed sensor is provided with a front plate of the sensor integral prism as a deflection unit, wherein both the transmitted light beams and the received light beams are deflected by one and the same prism. It can therefore come within the prism crosstalk between the transmission channel and receiving channel. In addition, a change between axial light emission and radial light emission is possible only with increased effort.

The EP 2 157 449 B1 discloses an optoelectronic sensor with a beam deflection by prisms, in which case a transmitting unit and a separate receiving unit are provided.

In principle, the transmitted light beams and the received light beams can be deflected by mirrors around the desired deflection angle. To produce such deflecting mirror but a Metallevampfung of plastic parts is necessary, which is associated with a relatively large effort and costs. In addition, there is an energy loss in the reflection of light on reflecting surfaces, so that the performance data of a sensor with radial light emission are usually worse than those of a sensor with axial light emission.

It is an object of the invention to reduce the manufacturing cost and to improve the efficiency in an optoelectronic sensor of the type mentioned.

The object is achieved by an optoelectronic sensor having the features of claim 1. According to the invention, at least one of the deflection optics comprises a prism having an interface whose surface normal has an angle of inclination to the main sensor direction, which is half the deflection angle.

Such a deflection prism can in the simplest case by a z. B. be made of plastic existing body with the cross-sectional area of an isosceles and right triangle, wherein the two mutually perpendicular surfaces form the inlet and outlet surfaces. The third surface serves as a reflective interface, with incident light totally reflected at an angle greater than the critical angle of total reflection. An advantage of the total reflection compared to a reflection on a metal layer is that ideally no energy losses occur. In addition, no complex coating processes are required for the production of a totally reflecting deflection prism. Furthermore, the beam deflection due to total reflection under ideal conditions is relatively insensitive to minor tilting of the prism, as they occur, for example, due to mounting tolerances. Ie. a misalignment of the prism within the sensor housing generally has little effect on the operation of the optical beam deflection. The prism can thus be slightly shifted, rotated or tilted relative to the transmitter or the receiver, without any significant limitation of the deflection function.

Consequently, no high demands are placed on the positioning of the prism, whereby the production of the optoelectronic sensor can be carried out particularly economically. Another advantage of the prism is that unwanted reflections on Tubus- or lens walls are at least partially decoupled, since the total reflection occurs only within a certain angular range.

According to one embodiment of the invention, the light passage area is an area perpendicular to the optical axes of the transmitter and the receiver, so that the boundary surface of the prism forms an angle with the light passage area, which is half of the deflection angle.

Within the housing itself, no beam deflection is preferably provided, that is, the transmitter radiates directly through the light passage surface.

Other developments of the invention are indicated in the dependent claims, the description and the accompanying drawings.

Preferably, at least one of the deflection optics is formed exclusively by a prism. In other words, no further optical components for beam deflection are present in this deflection optics except the prism. Thus, the manufacturing cost of the sensor can be kept very low.

According to one embodiment of the invention, a transmission optics designed in particular as a single lens for collimating transmitted light beams emitted by the transmitter is integrated into the housing and / or a receiving optical system designed in particular as a single lens for focusing received light beams onto the receiver is integrated into the housing. The transmitted light beams and / or the received light beams thus pass through the prism as a parallel bundle, so that an effective total reflection of all the light beams to be transmitted and / or to be received takes place. In addition, the transmission is maximum when the light rays impinge substantially perpendicular to the respective side surface of the prism.

According to a particularly advantageous embodiment of the invention, it is provided that the deflection module does not project beyond an outer surface of the housing in a radial direction with respect to the main sensor direction. This facilitates the mounting of the optoelectronic sensor, in particular in holes or mounting angles. Specifically, the optoelectronic sensor can be inserted from two sides into a corresponding bore or mounting angle.

According to a further embodiment of the invention, the first deflecting optics and the second deflecting optics are arranged such that the exit of the transmitted light beams from the deflecting module and the entry of the received light beams into the deflecting module take place spatially one behind the other in relation to the main sensor direction. This can be preferred over a configuration with deflection optics arranged next to one another with regard to the main sensor direction, given certain spatial requirements.

Furthermore, both the first and the second deflection optics may each comprise a prism, which in each case has an interface whose surface normal has an angle of the amount of half the deflection angle to the main sensor direction. There are no steaming needed.

According to a further embodiment of the invention, the prism of the first deflection optics by an air gap of the prism of second deflection optics separately. The two prisms are therefore preferably arranged as close to each other as possible, with a remaining, comparatively narrow air gap ensuring the occurrence of total reflection at the interface between the prisms. A closely adjacent arrangement of the two prisms makes possible, in particular, a space-saving design of the deflection module.

One of the two deflection optics may also comprise a mirror layer which is applied on an outer surface of the prism which forms the other deflection optics, the surface normal of which has an angle of inclination to the main sensor direction, which is half the deflection angle. In this embodiment, therefore, one of the deflection optics is realized by a prism and the other deflection optics by a mirror. This may be beneficial in certain applications. In particular, no air gap is required in such a configuration, which usually requires an exact adjustment of the corresponding components.

Preferably, the light passage surface is perpendicular to the longitudinal axis of the housing. In the elongated housing thus required for beam shaping components such as lenses and filters can be well accommodated. The deflection module ensures that the optoelectronic sensor can be mounted at installation sites with limited axial space, regardless of the length of its housing.

Furthermore, the deflection module can be in positive engagement with a mounting flange of the housing surrounding the light passage opening. The positive engagement ensures a secure fit of the deflection module on the housing and prevents misalignments. In addition, the interchangeability of the deflection module is facilitated and thus increases the flexibility of the optoelectronic sensor. For example, due to the mounting flange, it is easily possible to remove the deflection module and to replace it with a flat front pane. Thus, in a simple manner and with little effort a sensor with radial light emission can be transformed into a sensor with axial light emission or vice versa. In principle, the deflection module can also be permanently attached to the housing, for. B. welded to this, be. Even with such a configuration, a simple adaptation of the sensor to the conditions of the desired application is possible within the scope of the production of the sensor. In particular, the provision of a single housing type is sufficient to produce two different variants of sensors.

The housing is preferably cylindrical. However, it may also have a different cross-sectional shape instead of a circular cross-section, z. B. an elliptical, rectangular or polygonal cross-section.

According to a preferred embodiment of the invention, the housing is cylindrical and has an external thread formed at least in regions on the lateral surface of the cylindrical housing for mounting the optoelectronic sensor in an associated sensor receptacle. The external thread facilitates screwing the optoelectronic sensor into a corresponding, internally threaded sensor receptacle. Preferably, the outer diameter of the deflection module is smaller than the outer diameter of the external thread, so that the screwing of the optoelectronic sensor in the sensor receptacle from two sides is possible.

The invention will now be described by way of example with reference to the drawings.

1 is a sectional view of an optoelectronic sensor according to a first embodiment of the invention.

2 is a partial view of an optoelectronic sensor according to a second embodiment of the invention.

1 shows an embodiment of an inventive, designed as a photoelectric sensor optoelectronic sensor 11 , It comprises here a transmitting light beam emitting transmitter 13 and a receiving light beam receiving receiver 14 , which side by side in a common housing 25 are mounted. The transmitter 13 and the receiver 14 are in the illustrated embodiment on a common board 15 , At the transmitter 13 it may in particular be a laser diode or a light emitting diode. The recipient 14 is usually realized by a photodiode. However, a CCD or the like may be provided as a receiver.

As shown, the housing 25 designed as an elongated hollow cylinder and has a longitudinal axis L, which in this embodiment parallel to the emission direction of the transmitter 13 or the receive direction of the receiver 14 runs and coincides with the main sensor direction S. A front end face of the cylindrical housing 25 forms a light transmission surface D for the transmitted light beams and for the received light beams, which are each shown as arrows. In the example shown is inside the housing 25 no additional light deflection provided.

The light passage area D is an area assumed transversely to the main sensor direction S, which is not necessarily objective. In the example shown, the light passage area D is through the front opening of the housing 25 Are defined. However, the light passage surface D could also be defined by a front face of the housing occlusive front window of the cylindrical sensor housing.

In the example shown, the light passage area is perpendicular to the emission direction of the transmitter 13 and to the receive direction of the receiver 14 aligned. The optical axes of the transmitted light and the received light, which are to be understood in the present text that they correspond to the respective light propagation direction when passing through the light passage surface, thus correspond in the example shown, the transmission direction of the transmitter 13 or the receive direction of the receiver 14 , In this respect, in describing the embodiments of the 1 and 2 the terms optical axis OA1 and optical axis OA2 synonymous synonymous for the transmission direction of the transmitter 13 and the receiving direction of the receiver 14 inside the case 25 used.

A transmitter-side collimation lens 51 makes sure that from the transmitter 13 emitted transmitted light rays are collimated and pass through the light passage surface D as a parallel bundle. Similarly, a receiver-side focusing lens provides 53 for that, as a parallel bundle incident on receiving light beams to the receiver 14 be focused. Between the light passage surface D and the board 15 extends an intermediate wall 16 which separates the transmission channel from the reception channel and crosstalk between the transmitter 13 and receiver 14 prevented.

Also in the case 25 integrated is an only schematically illustrated electronic control unit 17 which serves the evaluation and generates, for example, an object detection signal. The object detection signal may be at one at the rear end surface of the cylindrical housing 25 provided electrical connection 21 be tapped. Via a setting potentiometer 19 , which of the light exit opposite side of the housing 25 is accessible, the scanning distance of the optoelectronic sensor 11 be set electronically.

To the transmission direction of the transmitter 13 and the receiving direction of the receiver 14 outside the case 25 , ie the monitoring direction Ü of the optoelectronic sensor 11 to tilt a deflection angle W from here 90 °, is a deflection module 29 provided, which has a first deflection optics in the form of a transmitter-side prism 37 and a second deflection optics in the form of a receiver-side prism 39 includes. The transmitter-side prism 37 and the receiver-side prism 39 are in a common module housing 31 integrated, which on the front face of the housing 25 is attached. For this purpose, a mounting flange is located in the area of the light passage surface D. 27 , which is a counterpart to one on the module housing 31 the deflection module 29 provided attachment section 33 forms. By a positive and optionally additionally non-positive engagement between the mounting flange 27 and the attachment portion 33 becomes a reliable seat of the deflection module 29 on the case 25 guaranteed. At the light exit and thus the area to be monitored facing side of the deflection 29 is a windshield 35 in the module housing 31 used.

The deflection module 29 Can also be permanently attached to the case 25 attached, z. B. welded to this, be. Even then, in the context of production, a simple adaptation of the sensor 11 to the circumstances of the desired application possible.

How out 1 shows are the transmitter-side prism 37 and the receiver-side prism 39 arranged immediately adjacent to each other and only through a narrow air gap 41 separated from each other. Preference is given to the transmitter-side prism 37 and the receiver-side prism 39 made of a plastic such as polymethyl methacrylate (PMMA) or polycarbonate (PC). These plastics have a relatively high refractive index. Concretely, in the case of PMMA, the refractive index is about 1.45 and in the case of PC about 1.58. In principle, prisms z. B. made of glass. The transmitter-side prism 37 and the receiver-side prism 39 each have one at an angle of 45 ° to the light transmission surface D extending interface 55a . 55b on. At the interface 55a the transmitter-side prism 37 be parallel to the optical axis OA1 of the transmitter 13 into the transmitter-side prism 37 entering transmitted light beams under total reflection by 90 ° deflects. Likewise, at the interface 55b of the receiver-side prism 39 perpendicular to the optical axis OA2 of the receiver 14 in the receiver-side prism 39 incoming received light beams deflected by total reflection by 90 °. The total reflection is in contrast to the reflection of a metal layer under ideal conditions without loss. By contrast, light beams deviating from a predetermined angular range are not totally reflected and thus do not reach the beam path provided for this purpose. In other words, due to the critical angle for total reflection, substantially only the useful light is reflected, not the stray light.

As the deflection module 29 as shown in radial direction with respect to the main sensor direction S, not over the outer surface of the cylindrical housing 25 survives, is the mounting of the optoelectronic sensor 11 especially easy. Should be provided with an enclosure for axial light emission 25 in which a windscreen in the through the mounting flange 27 If a recess formed on the light passage surface D is to be inserted, a light exit transverse to the main sensor direction S is desired, then in a simple manner within the scope of the production of the sensor 11 instead of the windscreen, the deflection module 29 be used. It is also possible, already used windscreen by the deflection 29 to replace or the deflection module 29 put on the existing windscreen. Thus it is possible to have one and the same housing 25 for two different types of optoelectronic sensors 11 namely, a sensor with axial light emission and a sensor with radial light emission to design.

In 2 an alternative embodiment of the invention is shown, in which instead of the receiver-side prism 39 a mirror layer 43 on a side surface of the transmitter-side prism 37 is provided. The mirror layer 43 can on the base material of the transmitter-side prism 37 be evaporated. In this variant eliminates the air gap. Nevertheless, due to the transmitter-side prism 37 to be reduced with a mirror layer to be evaporated total area. Likewise, energy losses in the reflection of mirror layers compared to an embodiment with two deflecting mirrors can be reduced, namely approximately halved in the ideal case.

In a non-illustrated embodiment of the invention, the deflection module is placed on the housing of an optoelectronic sensor, which is provided by default for an axial light emission and accordingly comprises a arranged on the light passage surface windshield. Due to the attached deflecting module, despite the housing provided for an axial light exit, a sensor with a radial light exit is available.

LIST OF REFERENCE NUMBERS

11

optoelectronic sensor

13

transmitter

14

receiver

15

circuit board

16

partition

17

electronic control unit

19

Setting potentiometer

21

electrical connection

25

casing

27

mounting flange

29

rerouting

31

module housing

33

attachment section

35

windscreen

37

transmitter-side prism

39

receiver-side prism

41

air gap

43

mirror layer

51

collimating lens

53

focusing lens

55a, 55b

interface

D

Light-transmitting surface

L

longitudinal axis

S

Main sensor direction

Ü

monitoring direction

OA1

optical axis of the transmitter

OA2

optical axis of the receiver

W

deflection

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The 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

• DE 10308085 B4 [0007]
• EP 2157449 B1 [0008]

Claims (11)

Optoelectronic sensor ( 11 ) for detecting objects in a surveillance area with an elongated housing ( 25 ), which has a front light passage surface (D) and defines by its longitudinal axis (L) a main sensor direction (S), a transmitter emitting light emitting beams ( 13 ), a receiving light beam receiving receiver ( 14 ), whereby the transmitter ( 13 ) and the recipient ( 14 ) in the housing ( 25 ) are arranged so that their optical axes (OA1, OA2) each deviate by at most 20 °, preferably at most 10 °, from the main sensor direction (S), the optical axes (OA1, OA2) being defined as those spatial directions into which the light propagation of the transmitted light beams or of the received light beams takes place with maximum intensity, and a deflecting module provided on the light passage surface (D) ( 29 ), which has a first deflection optics ( 37 ) for deflecting transmitted light rays passing through the light passage surface (D) and one of the first deflection optics ( 37 ) separately acting second deflection optics ( 39 . 43 ) for deflecting received light beams, which on the deflection module ( 29 ), wherein the deflection module ( 29 ) a tilting of the propagation directions of the transmitted light beams and the received light beams outside the housing ( 25 ) defined monitoring direction (Ü) relative to the main sensor direction (S) by a deflection angle (W) of not equal to 0 ° and preferably 90 ° causes, characterized in that at least one of the deflection optics a prism ( 37 . 39 ) with an interface ( 55a . 55b ) whose surface normal has an inclination angle to the main sensor direction (S), which is half the deflection angle (W). Optoelectronic sensor according to claim 1, characterized in that at least one of the deflection optics exclusively by a prism ( 37 . 39 ) is formed. Optoelectronic sensor according to claim 1 or 2, characterized in that a transmitting optics, in particular formed as a single lens ( 51 ) in the housing ( 25 ), which is used for collimating from the transmitter ( 13 ) emitted light beams is provided, and / or a particular designed as a single lens receiving optics ( 53 ) in the housing ( 25 ), which is provided for focusing received light beams on the receiver. Optoelectronic sensor according to at least one of the preceding claims, characterized in that the deflection module ( 29 ) in radial direction with respect to the main sensor direction (S), not over an outer surface of the housing ( 25 ) survives. Optoelectronic sensor according to at least one of the preceding claims, characterized in that the first deflection optics ( 37 ) and the second deflection optics ( 39 . 43 ) are arranged such that the exit of the transmitted light beams from the deflection module ( 29 ) and the entry of the received light beams in the deflection module ( 29 ) take place spatially behind one another with respect to the main sensor direction (S). Optoelectronic sensor according to at least one of the preceding claims, characterized in that both the first and the second deflection optics each have a prism ( 37 . 39 ) with an interface ( 55a . 55b ) whose surface normal has an inclination angle to the main sensor direction (S), which is half the deflection angle (W). Optoelectronic sensor according to claim 6, characterized in that the prism ( 37 ) of the first deflection optics through an air gap ( 41 ) of the prism ( 39 ) of the second deflection optics is separated. Optoelectronic sensor according to at least one of the preceding claims, characterized in that one of the two deflection optics is a mirror layer ( 43 ) formed on an outer surface of the prism ( 37 ) whose surface normal has an inclination angle to the main sensor direction (S), which is half the deflection angle (W). Optoelectronic sensor according to at least one of the preceding claims, characterized in that the light passage surface (D) at right angles to the longitudinal axis (L) of the housing ( 25 ) runs. Optoelectronic sensor according to at least one of the preceding claims, characterized in that the deflection module ( 29 ) with a mounting flange surrounding a front opening of the housing ( 27 ) of the housing ( 25 ) is in positive engagement. Optoelectronic sensor according to at least one of the preceding claims, characterized in that the housing ( 25 ) is cylindrical and an at least partially formed on the lateral surface of the cylindrical housing formed external thread for mounting the optoelectronic sensor in an associated sensor receptacle.

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