DE202006014925U1 - Optical sensor, for detecting objects, has a source of radiation for emitting light, an emitting lens, a detector, a detector lens and a protective front sheet - Google Patents

Abstract

A source (10) of radiation (SOR) emits light (12) guided by an emitting lens (14) onto an object (20) to be detected. A detector (30) detects light (22) reflected/scattered by the object and directed by a detector lens (34) onto the detector. A protective front sheet (40) in front of the emitting and detector lenses is translucent to light from the SOR and to the reflected/scattered light.

Description

The The present invention relates to an optical sensor according to the preamble of claim 1.

An optical sensor of the type mentioned and such a test method are in DE 196 31 059 A1 disclosed.

One generic optical Sensor for detecting objects comprises: a radiation source for emitting light, a transmitting optics for guiding the light an object to be detected, at least one detector for detection from the object reflected or scattered light, a detector optics for directing the reflected or scattered light to the detector and one mounted for protection from the transmitting optics and the detector optics Windscreen for the light of the radiation source and the object to be detected reflected or scattered light is at least partially transmissive.

at a test procedure for the degree of contamination of an optical detector is light on to be detected object of the object to be detected Reflected or scattered light is detected and it will Extra light used to reduce the level of pollution one for protection Check the front screen attached to the sensor optics of the sensor.

The Pollution of an optical front panel of a sensor has been so far only as an integral part of the total attenuation of the radiation. These include the dampings the optical radiation by misalignment in the transmission path and due the reflectance of the optical radiation reflecting Object, for example, a soiled reflector with reflection light barriers or a dark, low-radiation-reflecting object with reflection light sensors.

at For example, lightpickers with background suppression will be the signal attenuation by geometrical compensation of the signals of several receiver elements strongly suppressed, so that with increasing contamination of the windscreen after a long, apparently undisturbed Operation a sudden failure can be done with too much pollution. Because of the long compensated Pollution is a regular maintenance according to the actual Pollution degree hardly possible here.

DIN 44030 (Light barrier and light scanner terms and measuring methods) indicates the function reserve as the excess power, which falls on the light entrance surface and is evaluated by the receiver. As described above, the measurement of the functional reserve using neutral density filters described therein only detects the sum of the various influencing factors on the received light output and offers no approach for the separate detection of the contamination of the optical front screen.

A information about the degree of contamination of an optical front panel of an optoelectronic Sensors, such as a light barrier or a light sensor, is essential for the safe operation and optimum maintenance or cleaning of the sensors. This is especially the case in high dust applications, such as in printing machines or in the cement industry.

Next Pollution by dusty materials can also Wetting of the optical front panel with liquids for object detection used optical path of the optical sensor influence and thus impair its operational safety.

task The invention is to provide an optical sensor, in in particular, the soiling state of the optical front panel reliable can be determined.

In In a first aspect of the invention, this object is achieved by the sensor solved with the features of claim 1.

preferred embodiments the sensor according to the invention are the subject of the dependent Claims.

Of the Optical sensor of the above type according to the invention is characterized further developed that light of the radiation source and / or additional light an additional source for checking a Pollution degree of the windscreen can be coupled into the windscreen is and that the light coupled into the windscreen and / or Extra light on a variety of optical paths through the windscreen can be transmitted and then decoupled from the windscreen and in the detector or a separate additional detector quantitatively is detectable.

The Test method of the type described above is thereby developed, that the additional light is introduced into the windscreen so that the additional light several times on a front side of the windscreen internally is reflected and that the additional light then off The windscreen is coupled out and directed to a detector and is quantitatively demonstrated by this.

The core idea of the invention can be regarded as the additional light in the windshield couple in that it passes through the windscreen in a variety of ways, especially after a large number of reflections on the front of the windscreen, before it is decoupled from the windscreen again. In this way, on the one hand, a larger area of the windshield can be detected and, moreover, with only slight, but substantially homogeneous, pollution because of the multiple reflections, even these slight soiling can be detected.

The total transmitted through the windshield additional light can be both reinforced and dampened by pollution. For example, a gain occurs on, when normally exiting from the windscreen rays through reflective coverings, such as white Paper dust, are reflected back into the windscreen and thus get to the detector to detect the additional light. In addition, can possibly due to scattering on a not ideally smooth surface of the Windscreen occurring electromagnetic radiation due to dirt at least partially reflected and thus in addition to the internally reflected Receive light.

A attenuation The signal can occur when normally on the windscreen internally reflected light due to sufficiently transparent, optical Coverings with suitable refractive index associated with the windshield be brought to decoupling. For example, this may be due to liquid drops done on the windscreen.

at An advantageous variant of the invention is at least one separate Additional source available for sending additional light to check the Pollution degree of the windscreen. This additional source can then be specifically positioned so that any pollution can be detected very well. For certain constellations it may also be appropriate to provide a plurality of such additional sources.

In This relationship is particularly preferred when the additional source and / or the radiation source with respect to the windscreen so arranged is that the light and / or the extra light in the windscreen can be coupled and after several internal reflections on one Front of the windscreen can be disengaged from the windscreen and in the detector or a separate additional detector quantitatively is detectable.

Of the Transmitter and the receiver for the Radiation with which the contamination of the windshield has been detected will, can in principle arbitrary angles to each other. Also very large opening angle are, for example, on dirt particles on the windscreen Scattered radiation to be evaluated, in principle conceivable and can be beneficial in certain situations.

When Light for the object detection and as additional light is in preferred variants Infrared light used. This has the advantage of no disturbing visible Light pulses or reflections occur. It can, however, in principle also visible or possibly for Special applications, UV light can be used.

Such Sensors, such as light barriers or light sensors, can be realized cost-effectively be, if as the radiation source and as an additional source light-emitting diodes be used.

Of the according to the invention optical Sensor can also be a camera sensor or a vision sensor. in principle can the sensor of the invention in general for the detection of optically detectable structures, for example also for the proof of writing, serve.

Basically for the Extra light a completely separate transmitter-receiver arrangement chosen become. At a low cost Variant can while the detector and / or the additional detector photodiodes.

Of the Detector can basically also a multi-element detector, for example a CCD array. Hereby are also spatially resolved Measurements, for example triangulation measurements, possible. Of the Detector may also consist of several individual, in particular from each other consist of separate elements.

Of the Proof of the additional light and thus of contamination on the Windscreen is particularly reliable possible if possible no interaction between the object detection used Light and the additional light gives.

Conveniently, is therefore the additional Transmitter-receiver arrangement for the Additional light just arranged and aligned so that they to Object detection is not suitable, that is, they are the object, the Retroreflector or the transmitter, for example in the case of one-way photoelectric sensors, just not recorded. influences a misalignment and the reflectance of the object can on this way eliminates and the pollution of the windscreen can be recorded. Appropriately, therefore the supplemental source and / or the additional detector to avoid interactions from the radiation source and / or the detector through housing parts arranged separately, in particular in separate housing tubes, in housed a sensor housing be.

Especially Preferably, the additional transmitter and / or the additional detector are in one from the radiation source and / or the detector for object detection housed separate tube. To the actual object detection not to influence, while the beam paths of additional Transmitter-receiver arrangement through separate tubes from the transmitters used for object detection or recipients separated. This is favored by that the additional light is generally under very shallow entrance or exit angle in the windscreen on or is discharged. Such flat entrance and exit angles are at the beam paths the transmitter and receiver used for object detection usually not given.

The Pollution detection and object detection can by different frequencies or phase positions of the signals or Different sampling times for both tasks even better be separated from each other. For example, the intensity of the light and / or of the additional light can be modulated.

A Separation of object detection and contamination detection is special easy in a variant of the sensor according to the invention possible at the radiation source and the additional source with different Phase position and / or different frequency can be modulated. In terms of apparatus, it is then appropriate that the individual Modulating the intensity of the light and / or the additional light, a drive device for the radiation source and / or the supplemental source is present.

Finally, can the additional transmitter totally asynchronous to the transmitter for the object detection, thus to the Radiation source, be modulated.

It is then possible for example the pollution detection only one additional transmitter, so the additional source, and to prove the additional light also for the proof of object to use the detector used.

at Such a variant of the method is thus the one to be proved Object reflected or scattered light and that through the windscreen transmitted additional light detected by the same detector, so that the structure of the sensor are kept simpler overall can.

One particularly compact optical design of the sensor is achieved if the windscreen has at least one optical image forming the optical image Element, such as a lens or a diffractive element, such as a grid containing. For example, the additional light to be evaluated, the intensity of which a possible Pollution deposit on the windscreen is changed by a suitable curved collected reflective element and the detector or the Additional detector are routed.

Especially for the If only a single detector is used, it is expedient to use the additional light with the help of a mirror to guide this detector.

at a particularly preferred embodiment, which is a high variability of the bodywork is for guiding the auxiliary light to the windscreen and / or for conducting additional light emerging from the windshield at least one optical fiber is present on the detector or the additional detector. For compact and reliable working embodiments the sensor according to the invention is the light guide for collecting and directing by a possible Dirt on the windshield intensity changed additional light on the detector or the additional detector integral part the windscreen, the detector or the auxiliary detector.

advantageous Properties with regard to the proof of contamination can also be achieved when the windscreen is intended for selective coupling or decoupling the additional light with at least one local structuring, wherein it is for example a coating or a roughening can act is provided. By such a suitable structuring of zones, especially on the inside of the windscreen, is a decoupling and evaluation of radiation beams of the additional light allows not without the said structuring due to the angle of incidence would be disconnected the windscreen would not leave.

Farther can be such structuring, especially on the inside the windscreen, also serve to additional diffuse radiation components to generate their reflection on possibly on the outside the front side dirt with the help of the detector or the additional detector can be received and evaluated.

The Sensitivity of the optical arrangement to wetting of the windscreen with liquid drops can over it increased when the internal reflections of the additional light in the windscreen nearly or completely Total reflections are. The additional light must then in a corresponding flat angle relative to the surface of the windscreen in the Windscreen can be coupled.

The Pollution detection described does not necessarily continuous but can, for example, only on external request out, for example by an operator or a machine control, carried out become. Only on request then the additional source is turned on and the proven intensity of the additional light evaluated.

A information about Type and degree of pollution can be obtained when using a window comparator a deviation of the intensity of the additional light is determined by a setpoint determined with a clean optical front surface. At a certain level becomes such a deviation then assessed as pollution.

Conveniently, not only can a simple distinction between cleaner and dirty optical windscreen, but based on of measure the signal change can differentiate between different categories of pollution, such as light, substantial and critical pollution become.

at a variant of the method in which the intensity of the through the windscreen transmitted additional light evaluated and with regard to different Pollution categories is evaluated, is a targeted maintenance and cleaning possible.

With a window comparator, the detector or the additional detector In particular, both a signal increase and a signal attenuation be detected in the beam path of the additional light. Also from this can an information about the type of contamination, such as wetting by a liquid or adhering dust particles are recovered.

In device-wise is then to evaluate the detected additional light an evaluation with a window comparator available.

Especially can come from a change of intensity the transmitted additional light also obtained information be over the wetting of the windscreen, for example, with condensation or Rainwater, or a possible Icing of the windscreen. For example, a condensation or Icing state of optoelectronic sensors in cold stores be determined. Here you can Water droplets or frost affect the proper functioning of the sensor, so that an internal or external heating of the sensor or in any case, the optical front window is necessary. The intensity of through The front screen transmitted additional light can therefore be used as an indicator for one Wetting or icing of the windscreen and in particular also be used to control a windscreen heater.

Especially can be advantageous the sensors according to the invention Furthermore used in printing machines.

at a particularly compact variant of the sensor according to the invention the transmitting and the detector optics have common optical elements and it is a beam splitter for separating transmit and detector beam paths available. For example, you can the common optical elements part of an autocollimation optics be. The beam splitter, which is for separating from the radiation source can be sent and detected by the detector light, can partially or semi-permeable Be a mirror. In addition to spatial Advantages and the structure with fewer components are characterized by such Variants in particular characterized in that essentially no blind area is present and realizes sensors with reach of virtually zero can be.

Further Advantages and features of the sensor according to the invention are described below with reference to the attached Figures explained.

Here in demonstrate:

1 a schematic view of a first embodiment of a sensor according to the invention;

2 a schematic view of a second embodiment of a sensor according to the invention;

3 another view of the sensor 1 with drops of liquid on the windscreen;

4 another view of the sensor 1 with dirt particles on the windscreen;

5 a schematic and sectional detail view of the windscreen; and

6 another schematic and sectional detail view of the windshield with a dirt particle.

A first embodiment of the sensor according to the invention and the test method according to the invention will be described with reference to FIGS 1 such as 3 and 4 explained. Equivalent components are provided with the same reference numerals in the figures as a whole.

The in the 1 . 3 and 4 shown sensor 100 has as essential components a radiation source 10 , a transmission optics 14 , a detector 30 with a detector optics 34 and a windshield 40 on, to protect the transmitting optics 14 and the detector optics 34 is arranged in front of these components. According to the invention are also an additional source 80 and an additional detector 60 available.

The sensor according to the invention operates as follows: The radiation source 10 sends light 12 from that indicated by the stylized lens transmission optics 14 along an optical axis 16 first by the one for the light 12 transparent windscreen 40 and subsequently to a proven object 20 is directed. from the object to be detected 20 thrown back, so reflected or scattered light 22 , passes through the front screen again after passing through 40 on the also represented by a stylized lens detector optics 34 with an optical axis 36 , The detector optics 34 conducts the light reflected or scattered by the object to be detected 22 on the detector 30 where it is detected.

The additional source 80 sends additional light illustrated by arrows 82 out, which at a shallow angle in the windscreen 40 is coupled. After a lot of internal reflections on one front 42 and a back 44 the windscreen 40 the additional light comes on 82 again from the windscreen 40 out, meets an additional detector 60 and is detected by this quantitatively. A small part of the additional light 82 Occurs at every reflection process from the windscreen. The internal angle of incidence of the additional light 82 on through the front 42 the windscreen 40 Therefore formed interface is therefore close to the angle of incidence for total reflection, but this does not quite reach. This configuration has the advantage that, albeit small, by arrows 83 illustrated radiation components coming out of the windscreen 40 at each reflection process leak on any dirt on the windscreen 40 can react. Such a constellation is in 4 represented where two schematically illustrated pollution particles 72 . 74 directly on or slightly spaced in front of the windshield 40 are located.

The from the windscreen 40 emerging radiation components, illustrated by arrows 83 , be of these particles 72 . 74 thrown back and thus arrive, exemplified as an arrow 86 , also on the detector 60 ,

The contamination particles thus lead to an increase in the detector 60 proven intensity.

If it comes to a wetting of the front 42 the windscreen 40 with liquid drops 70 as shown schematically in 3 shown, occurs due to the changed refractive indices at the optical interface more additional light from the windscreen 40 out. These lights are in 3 through arrows 84 shown. After emerging from the liquid drops 70 with renewed refraction this light leaves, represented by arrows 85 , the sensor 100 and thus can no longer by detector 60 be detected. A reduction of the detector 60 proven intensity thus indicates a wetting of the front 42 the windscreen 40 out.

At the in 2 example shown is the additional light 82 through a mirror 90 on the detector 30 , which is also used for proof of object, steered. That on the detector 30 Mirrored additional light is by an arrow 92 shown. In this variant, fewer components are therefore required in the optical design. However, those in the detector must be 30 detected signals, for example by appropriate modulation of the light 12 and the additional light 82 to be separated. Incidentally, the function corresponds to the in 2 illustrated variant of that in the 1 such as 3 and 4 shown example.

Details of the reflection of the additional light 82 inside the windscreen 40 be based on the schematic 5 and 6 explained.

In 5 is shown as that in the windshield 40 entering additional light 82 in the fields of 43 on the front side 42 as well as in the area 45 at the back 44 the windscreen 40 is reflected. The windscreen 40 is at the back 44 in the area 46 also with a structuring 50 , For example, a coating or a roughening provided that a defined decoupling of the additional light 82 from the windscreen 40 allows.

Another application of such structuring 50 is in 6 shown. There arise through the structuring 50 additional, by arrows 87 represented light components from the windscreen 40 leak due to the changed angle of incidence on the interface and on any existing pollution particles 72 can react. From the pollution particle 72 back-reflected or scattered light 88 can then as a signal increase in the detector 30 be detected.

The present invention provides a novel optoelectronic sensor for detecting objects, which can operate, for example, as a light barrier or as a light scanner. The sensor 30 has at least one transmitter element and / or at least one receiver element, which are arranged in a housing. For the passage of the radiation to the outside and to the object as well as to the entry of the object reflected or scattered radiation in the sensor and the receiver element, the housing is provided with an optical front panel.

Of the Sensor further has at least one further transmitter element and optionally also a further receiver element. Within The windscreen reflected radiation is detected and a possible reinforcement or mitigation as a result of additional Reflection on dirt particles or decoupling due to reflective or wetting coverings can as a measure of the amount and the kind of pollution of the windscreen by just this undesirable Coverings evaluated become.

Claims (16)

Optical sensor for detecting objects with a radiation source ( 10 ) for emitting light ( 12 ), with a transmission optics ( 14 ) for guiding the light ( 12 ) to an object to be detected ( 20 ), with at least one detector ( 30 ) for the detection of the object ( 20 ) reflected or scattered light ( 22 ), with a detector optics ( 34 ) for guiding the reflected or scattered light ( 22 ) on the detector ( 30 ), and with a protection against the transmission optics ( 14 ) and the detector optics ( 34 ) mounted windscreen ( 40 ), which are responsible for the light ( 12 ) of the radiation source ( 10 ) and the object to be detected ( 20 ) reflected or scattered light ( 22 ) is at least partially permeable, characterized in that the light ( 12 ) of the radiation source ( 10 ) and / or additional light ( 82 ) an additional source ( 80 ) for checking a degree of contamination of the windscreen ( 40 ) in the windscreen ( 40 ) can be coupled and that in the windscreen ( 40 ) coupled light ( 12 ) and / or additional light ( 82 ) on a variety of optical paths through the windscreen ( 40 ) transmissibly and subsequently out of the windscreen ( 40 ) and in the detector ( 30 ) or a separate additional detector ( 60 ) is quantitatively detectable. Sensor according to claim 1, characterized in that a separate additional source ( 80 ) is present for emitting additional light ( 82 ) for checking the degree of soiling of the windscreen ( 40 ). Sensor according to one of claims 1 or 2, characterized in that the additional source ( 80 ) and / or the radiation source ( 10 ) with respect to the windscreen ( 40 ) is arranged so that the light ( 12 ) and / or the additional light ( 82 ) in the windscreen ( 40 ) and after several internal reflections on a front side ( 42 ) of the windscreen ( 40 ) and in the detector ( 30 ) or a separate additional detector ( 60 ) is quantitatively detectable. Sensor according to one of claims 2 or 3, characterized in that the additional source ( 80 ) and / or the additional detector ( 60 ) to avoid interactions from the radiation source ( 10 ) and / or the detector ( 30 ) arranged separately by housing parts, in particular in separate housing tubes, are housed in a sensor housing. Sensor according to one of claims 1 to 4, characterized in that the light ( 12 ) and the additional light ( 82 ) Infrared light is. Sensor according to one of claims 1 to 5, characterized in that for individually modulating an intensity of the light ( 12 ) and / or the additional light ( 82 ) a drive device for the radiation source ( 10 ) and / or the additional source ( 80 ) is available. Sensor according to one of claims 1 to 6, characterized in that the windscreen ( 40 ) for targeted coupling or decoupling of the additional light ( 82 ) with at least one local structuring ( 50 ) is provided. Sensor according to one of claims 1 to 7, characterized in that the structuring ( 50 ) is a coating or a roughening. Sensor according to one of claims 1 to 8, characterized in that for conducting the additional light ( 82 ) on the detector ( 30 ) or the additional detector ( 60 ) an optical element, in particular a mirror ( 90 ), is available. Sensor according to one of claims 1 to 9, characterized in that for conducting the additional light ( 82 ) on the windscreen ( 40 ) and / or for guiding from the windscreen ( 40 ) exiting additional light ( 82 ) on the detector ( 30 ) or the additional detector ( 60 ) at least one light guide is present. Sensor according to one of claims 1 to 10, characterized in that for evaluating the detected additional light ( 82 ) An evaluation device with a window comparator is present. Sensor according to one of claims 1 to 11, characterized in that the internal reflections of the additional light ( 82 ) in the windscreen ( 40 ) are approximately or completely total reflections. Sensor according to one of claims 1 to 12, characterized in that the radiation source ( 10 ) and the additional source ( 80 ) Are light-emitting diodes. Sensor according to one of claims 1 to 13, characterized in that the detector ( 30 ) and / or the additional detector ( 60 ) Are photodiodes. Sensor according to one of claims 1 to 14, characterized in that the transmitting optics ( 14 ) and the detector optics ( 34 ) have common optical elements and that a beam splitter for separating transmit and detector beam path is present. Sensor according to one of claims 1 to 15, characterized in that for separating object detection and contamination detection, the radiation source ( 10 ) and the additional source ( 80 ) can be modulated with different phase position and / or different frequency.