DE102006045916B4 - Light sensor or light barrier for the detection of objects and test methods for the degree of soiling of a light sensor or a light barrier - Google Patents

Abstract

Light sensor or photocell for the detection of objects,
with a radiation source (10) for emitting light (12),
with a transmission optical system (14) for guiding the light (12) onto an object (20) to be detected,
with at least one detector (30) for detecting light (22) reflected or scattered by the object (20),
with detector optics (34) for directing the reflected or scattered light (22) onto the detector (30),
with a front screen (40) attached to protect it from the transmission optics (14) and the detector optics (34) and transparent to the light (12) of the radiation source (10) and the light (22) reflected or scattered by the object (20) to be detected is and
with a separate additional source (80) for emitting additional light (82) for checking a degree of contamination of the windshield (40),
characterized,
the additional source (80) is arranged with respect to the front screen (40)
that the additional light (82) can be coupled into the front screen (40) and ...

Description

The The present invention relates to a light sensor or a light barrier according to the preamble of claim 1.

In addition, refers The invention relates to a test method for the degree of contamination of a windshield a light sensor or a light barrier for the detection of objects according to the preamble of claim 13.

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

One generic light scanner or a generic light barrier for the detection of objects indicates: A radiation source for emission of light, a transmitting optics for directing the light to be detected Object, at least one detector for detecting reflected from the object or scattered light, a detector optics for guiding the reflected or scattered light on the detector, one for protection from the Transmitting optics and the detector optics attached windscreen, which is responsible for the light the radiation source and the object to be detected reflected or scattered light permeable is and an additional source for emitting additional light for checking a Pollution degree of the windscreen.

at a generic method Light is directed to an object to be detected, from the detected Object reflected or scattered light is detected and additional light is used to reduce the level of contamination of a Protection against sensor optics of the light sensor or the light barrier checked windscreen to check.

The Contamination of an optical front panel of a light scanner or A photocell has so far only been an integral part the overall weakening the radiation detected. These include the attenuation of the optical radiation Misalignment in the transmission path as well as due to the reflectance of the optical radiation reflective object, such as a dirty reflector with reflection light barriers or a dark, only little radiation reflective object in 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 functional reserve as the surplus power which is on the light entry surface falls and from the recipient Is evaluated. The measurement of the functional reserve described there detected by neutral density filters, as described above, only the sum of the various influencing factors on the received Light output and offers no approach to separate detection of pollution 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 beam path of the light sensor or the light barrier and thus impair its operational safety.

Further light sensors or light barriers are described in DE 102 54 888 B4 . DE 196 29 396 A1 . US 5,668,366 . DE 103 56 704 B4 . EP 527 326 A1 . DE 199 46 220 C1 and DE 42 40 395 C2 ,

DE 195 30 289 A1 discloses a sensor for visibility and rain cover detection, which warns the driver at not visibly adjusted driving speed.

DE 10 2004 015 040 A1 describes a camera in a motor vehicle with an image sensor, wherein the camera primary functions such as night vision support, lane departure warning, traffic sign recognition and / or reversing aid by detecting the optical radiation of the traffic space surrounding the motor vehicle and a rain sensor function provides.

EP 1 507 138 A2 The object of the invention is an image processing system which detects matter of foreign origin on a pane of the vehicle with high reliability.

In DE 102 61 923 A1 a sensor device for detecting the wetting of a transparent pane is described. In this case, the radiation emitted by a transmitter is in the disk coupled and dependent on the wetting of the disc part of the guided under total reflection in the disc, coupled radiation is coupled out at least one surface of the disc from the disc and fed to a receiver.

task The invention is a light sensor or a light barrier to provide, in or at the pollution state the optical front panel can be determined particularly reliable. Furthermore should be a particularly reliable Test procedure for the degree of soiling of a light sensor or a light barrier be specified. In a first aspect of the invention, this becomes Task by the light scanner or the light barrier with the features of claim 1.

In A second aspect of the invention is achieved by the test method solved with the features of claim 13.

preferred embodiments and advantageous variants of the method according to the invention are the subject the dependent Claims.

in the Subsequently, a light sensor or a photoelectric sensor also becomes short referred to as optical sensor. The optical sensor of the above type is according to the invention further developed that the additional source with respect to the windscreen arranged so is that the additional light can be coupled into the windscreen and after several internal reflections on a front of the windscreen off the windscreen disengageable and in the detector or a separate Additional detector is quantitatively detectable and that the transmitter-receiver arrangement for the Additional light is arranged and aligned so that an object detection is excluded with the additional light.

The Test method of the type described above is according to the invention by further developed that the additional light so introduced into the windscreen That is, the auxiliary light is repeatedly on a front of the windscreen is reflected internally and that the additional light then off The windscreen is coupled out and directed to a detector and is quantitatively demonstrated by this.

When Core idea of the invention can be considered, the additional light into the windshield so that there is a variety by going through reflections on the front before it's out of the back Windscreen is disengaged. In this way, on the one hand larger area The windscreen can be detected and also can be at low, however essentially homogeneous pollution due to multiple reflections as well this low pollution 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.

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, of dirt particles on the windscreen scattered radiation is to be evaluated, possible and may be advantageous.

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 Detector can basically also a multi-element detector, for example a CCD array. With such detectors can especially spatially resolved Measurements, such as triangulation measurements, are performed. The detector may also consist of several individual, in particular of each other consist of separate elements.

In principle, the optical sensor according to the invention can also be a camera sensor or a vision sensor. In principle, the optical sensor according to the invention can generally be used for Weis of optically detectable structures, for example, for the detection of writing serve.

Basically for the Extra light a completely separate transmitter arrangement selected become. At a cost-effective Variant may be the detector is a photodiode.

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 re flexionsgrads 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 thereby especially easy, that the radiation source and the additional source with different Frequency are modulated. In terms of apparatus is then appropriate that for individual modulation of the intensity of the light and / or the additional light a drive device for the radiation source and / or the additional 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.

The reflected or scattered light from an object to be detected and the transmitted through the windscreen additional light Thus, with the same detector detected, so that the structure of the Sensors can be kept simpler overall.

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 directed to the detector become.

in this connection the additional light is directed to the detector by means of a mirror.

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. For compact and reliable working embodiments of the inventive sensor is the light guide for collecting and passing the through a possible contamination coating on the windshield changed in intensity Additional light on the detector integral part of the windscreen or the detector.

Advantageous properties with regard to the proof of contamination can also be achieved if the windshield is provided for selectively coupling or decoupling the additional light with at least one local structuring, which can be, for example, a coating or a roughening. By such a suitable structuring of zones, in particular dere on the inside of the windscreen, a decoupling and evaluation of radiation beams of the additional light is made possible, which would not be decoupled without the said structuring due to the angle of incidence, would not leave the windscreen.

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 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 optics and the detector optics have common optical Elements and there is a beam splitter for separating transmission and detector beam path available. Common optical elements can For example, be provided as part of a autocollimation optics. Of the Beam splitter, which is for separating from the radiation source sent and light to be detected by the detector may be a partial or semipermeable Be a mirror. In addition to spatial Advantages and the structure with fewer components are characterized by such Sensor variants in particular characterized in that essentially no Blind area is present and therefore sensors with a range of practically zero can be realized.

Further Advantages and features of the sensor according to the invention and the test method according to the invention will be explained below with reference to the accompanying figures.

Here in demonstrate:

1 a schematic view of an embodiment of a sensor with a second detector;

2 a schematic view of an 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 , an additional detector 60 , 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. It is also an additional source 80 available.

The sensor works 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 an object to be detected 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 shown by a stylized lens Detek toroptik 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 The sensor according to the invention 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. Across from 1 Thus, fewer components are needed in the optical design. However, those in the detector must be 30 detected signals by appropriate modulation of the light 12 and the additional light 82 be separated. Incidentally, the function of the in 2 shown sensor 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. Within the windscreen reflected radiation is detected and a possible reinforcement or weakening 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 be evaluated.

Claims (16)

Light sensor or light barrier for the detection of 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 ), 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 permeable, and with a separate supplementary source ( 80 ) for emitting additional light ( 82 ) for checking a degree of contamination of the windscreen ( 40 ), characterized in that the supplementary source ( 80 ) with respect to the windscreen ( 40 ) is arranged so that the additional light ( 82 ) in the windscreen ( 40 ) and after several internal reflections on a front side ( 42 ) of the windscreen ( 40 ) from the windscreen ( 40 ) and in the detector ( 30 ) is quantitatively detectable that the transmitter-receiver arrangement for the additional light is arranged and aligned so that an object detection is excluded with the additional light that for guiding the additional light ( 82 ) on the detector ( 30 ) a mirror ( 90 ) and that the intensities of the radiation source ( 10 ) emitted light and emitted by the additional source additional light ( 82 ) are modulated with different frequency. Light sensor or light barrier according to claim 1, characterized in that the additional source ( 80 ) 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. Light sensor or light barrier according to one of claims 1 or 2, characterized in that the light ( 12 ) and the additional light ( 82 ) Infrared light is. Light sensor or light barrier according to one of claims 1 to 3, characterized in that for the individual modulation of 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. Light sensor or light barrier according to one of claims 1 to 4, 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. Light sensor or light barrier according to one of claims 1 to 5, characterized in that the structuring ( 50 ) is a coating or a roughening. Light sensor or light barrier according to one of claims 1 to 6, 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 ) at least one light guide is present. Light sensor or light barrier according to one of claims 1 to 7, characterized in that for evaluating the detected additional light ( 82 ) An evaluation device with a window comparator is present. Light sensor or light barrier according to one of claims 1 to 8, characterized in that the internal reflections of the additional light ( 82 ) in the windscreen ( 40 ) are approximately or completely total reflections. Light sensor or light barrier according to one of claims 1 to 9, characterized in that the radiation source ( 10 ) and the additional source ( 80 ) Are light-emitting diodes. Light sensor or light barrier according to one of claims 1 to 10, characterized in that the detector ( 30 ) is a photodiode. Light sensor or light barrier according to one of claims 1 to 11, 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. Test method for the degree of soiling of a windshield of a light scanner or a light barrier for the detection of objects according to one of claims 1 to 12, in which light ( 12 ) of a radiation source ( 10 ) with a transmission optics ( 14 ) to an object to be detected ( 20 ), in which the object to be detected ( 20 ) reflected or scattered light ( 22 ) with a detector ( 30 ) and in the additional light ( 82 ) is used to reduce the degree of soiling that protects against sensor optics of the light sensor or photocell ( 100 ) mounted windscreen ( 4 ), with the windscreen for the light ( 12 ) of the radiation source ( 10 ) and the object to be detected ( 20 ) reflected or scattered light ( 22 ) is permeable, characterized in that the additional light ( 82 ) so in the windscreen ( 40 ), that the additional light ( 82 ) several times on a front side ( 42 ) of the windscreen ( 40 ) is reflected internally and that the additional light ( 82 ) then from the windscreen ( 40 ) is coupled to the detector ( 30 ) and quantitatively demonstrated that the intensities of the additional light ( 82 ) and the light ( 22 ) and that the radiation source ( 10 ) and the additional source ( 80 ) are modulated with different frequency. Method according to claim 13, characterized in that the additional source ( 80 ) only on, in particular external, request turned on and the proven intensity of the additional light ( 82 ) is evaluated. Method according to one of claims 13 to 14, characterized in that the intensity of the through the windscreen ( 40 ) transmitted additional light ( 82 ) and evaluated against different categories of pollution. Method according to one of claims 13 to 15, characterized in that the intensity of the through the windscreen ( 40 ) transmitted additional light ( 82 ) as an indicator of wetting or icing of the windscreen ( 40 ) and used to control a windscreen heater.