DE102009023615A1 - Measuring device, measuring system and method for measuring the contamination of a transparent measuring object - Google Patents

Abstract

A measuring device (20) for measuring the contamination of a light-transmitting measuring object (7) comprises a radiation source (1), a coupling device (3) for coupling a beam (2) into the measuring object (7), so that the beam (2) in the measuring object ( 7), a decoupling device (5) for decoupling the beam (2) from the measurement object (7), a radiation detector (6) and a comparison device (10), which is designed, a characteristic value of the detected beam (2) with a Reference value to compare.

Description

The The invention relates to a measuring device, a measuring system and a Method for measuring the contamination of a transparent measuring object.

Translucent materials Among other things, as covers for lighting devices used. The cover may protect and / or protect the lighting device influence the emission characteristics. That of the lighting device radiated light at least partially penetrates the cover. Another application for translucent Materials are windowpanes.

By environmental influences can the surfaces of translucent objects pollute. With increasing pollution, the light transmission becomes reduced. For windows, the transparency is deteriorated. at Covers for lighting equipment If there is more pollution, less light can penetrate the cover.

This A problem occurs inter alia in traffic tunnels, their lighting equipment usually with a glass or Acrylic glass cover are provided; but also other materials are conceivable. These covers are made, among other things, by car exhaust and tire wear dirty and therefore need regular cleaning be subjected to the adequate lighting of the tunnel guarantee. To optimize the cleaning interval is a monitoring Pollution degree desirable.

It is therefore the task, a device and a method to provide for measuring the contamination of a translucent object to be measured.

The Problem is caused by a measuring device for measuring contamination a translucent DUT solved with the features of claim 1. Further a measurement system and a method of measurement are provided.

The Measuring device for measuring the contamination of a transparent measuring object comprises a radiation source, a coupling device for coupling of a beam into the measurement object, so that the beam in the measurement object guided is, a decoupling device for decoupling the beam the measuring object, a radiation detector and a comparison device, which is formed with a characteristic value of the detected beam to compare a reference value.

The Measuring device is suitable for contamination, in particular surface contamination, of To detect the object to be measured.

Under "translucency" is the ability understood the material, electromagnetic waves, such as light in the visible spectral range, to pass through the material. This property is also called transparency. Under "translucency" also falls, that only a part of the electromagnetic waves is transmitted.

A Radiation source is a source for providing electromagnetic Radiation, in particular light, for example in the visible range. light may also include ultraviolet or infrared radiation.

Of the Beam is for example a radiation beam, ie a group of Rays of radiation that propagate in a preferred direction. The beam may be, for example, a light beam.

The Einkoppeleinrichtung allows to couple a beam into the measurement object, so that it is in the Test object guided will, that is the beam is running within the test object.

Of the Radiation detector is a sensor that is designed a characteristic value of the decoupled beam. An embodiment of the radiation detector is a light detector. In the detected Characteristic value can be, for example, the light intensity or power act. The comparison device compares the detected characteristic value with a comparative value. Based on the comparison can be determined whether a cleaning of the test object is required or Not. In one embodiment is only determined and displayed, if a cleaning required is or not. In an alternative embodiment, the comparison result a value from a continuous or discrete value range, which indicates the degree of contamination.

The beam is guided in the test object. Preferably, the beam is coupled in such a way that the beam in the measurement object is reflected at least once on one side of the measurement object, that is thrown back after passing through the measurement object from one side of the measurement object into the measurement object. This is advantageously a total reflection, so that no partial transmission in the reflection but only absorption effects attenuate the beam as it passes through the measurement object. In the case of a measurement object having a top and bottom side, the beam can travel in a zigzag pattern from the coupling device to the coupling-out device in the measurement object when the beam is alternately reflected at the top and bottom side. Thus, the beam by total reflection in the measurement object is similar to ei nem light guide out of the coupling to the coupling device. Dirt on one side of the DUT attenuates the light on reflection on that side. With increasing pollution, the damping increases. As the number of reflections on a dirty side increases, the attenuation of the beam increases. Even less contamination can be reliably detected, since the damping is increased by multiple reflection, which facilitates the detection.

In an advantageous embodiment include the coupling device and / or the decoupling a prism. The prism in the Coupling device is suitable for the provided by the radiation source Redirecting the beam so that it is coupled into the object to be measured and after passing through the test object on one side of the The object being measured is totally reflected. The prism in the decoupling device is suitable to deflect the decoupled beam so that he led to the radiation detector becomes.

advantageously, The coupling devices and / or the coupling devices comprise a Silvering. The mirror coating is advantageously at one Side of the coupling device and / or the decoupling device applied, at the beam within the coupling device and / or the Decoupling device is reflected or can be reflected, if he by the coupling device or through the Outcoupler propagated. The mirroring helps transmission or damping effects to avoid. This results in a signal improvement of the einzkoppelnden or decoupled beam.

advantageously, include the input device and / or the output device a light leader Element through which the electromagnetic wave, in particular light, runs, wherein the refractive index of the element is similar to the refractive index of the DUT is. The coupling or decoupling of the Ray occurs at the transition leading from the light Element in the measurement object. If the refractive index of the element is similar to the Refractive index of the measuring object is, reflection or refraction of the beam at the transition avoided or reduced. The refractive index of the element and the refractive index of the measurement object are advantageously such coordinated so that the beam is coupled so that he is totally reflected in the measurement object. When the coupling device and / or the decoupling device are glued to the measurement object, For example, an adhesive used for this purpose advantageously has a similar one Refractive index as the coupling device and / or the decoupling device and the measurement object.

In an advantageous embodiment, the coupling devices and / or the decoupling devices against light irradiation of Ambient light shielded. Under ambient light is any external Light irradiation to the measuring device understood, for example Daylight. If the measurement object is the cover of a lighting device is the light emitted by the illumination device or that radiated from adjacent lighting devices Light ambient light. When the coupling and decoupling near the lighting device are positioned, that of the Light source emitted light can lead to falsification of the measurement. The Shielding helps to prevent the ambient light from measuring falsified. This would be the Case when the ambient light over the DUT and the decoupling device would be guided to the radiation detector.

A Possibility, largely eliminate the influence of ambient light during the measurement, is the use of a radiation source that is suitable amplitude modulated To provide light. In one embodiment, the light signal is on periodic sinusoidal signal. An embodiment of an amplitude modulated Signal is an amplitude-shifted light signal. The amplitude-keyed Light signal has two levels, between which switched back and forth becomes. In the simplest case the light signal is a periodic on-off-keyed one Signal with pulses, as by turning on and off the radiation source can be generated. In an alternative signal is only a single one Impulse provided. Another alternative signal has a sequence of pulses.

Of the Radiation detector is advantageously formed to an intensity or intensity change detect, for example, a light intensity or light intensity change. The radiation detector provides an output signal that depends on the detected intensity or intensity change is. When using amplitude modulated signals, the radiation detector is advantageously designed to detect the change in intensity. Constant ambient light is not taken into account in this detection. This allows the pollution measurement even in daylight or to perform at a lighting device during their operation.

In an alternative embodiment generates the radiation source a narrow band light signal, by using a bandpass filter can be detected in the radiation detector. This bandpass filter filters out broadband ambient light.

A measuring system includes a translucent ges measuring object and a measuring device, such as described above, the coupling device and the coupling device are positioned on a same side or different sides of the measuring object, which has a first and a second side.

If the object under test has a side that is more exposed to pollution is as the other, as for example on the outside a lighting source cover in a tunnel is the case, Thus, the coupling device and the decoupling device are advantageously mounted on the side that is not exposed to pollution. Thus, the pollution of the measuring device is avoided, which could influence the measurement. Of the Radiation detector is through the measurement object, for example in the case of Cover, against environmental influences and dirt protected.

Around It may be an advantage to facilitate access to the measuring equipment be the measuring device on the more polluting side too position. Alternatively you can the coupling device and the coupling device on different Be positioned sides of the measuring object.

advantageously, the coupling device and the coupling device are so positioned so that the beam is reflected several times. This increases the measurement accuracy, because the contamination of the test object due to the multiple reflection multiple into the measurement, so local deviations of the degree of pollution are not so strongly affect the measurement result.

In a method for measuring the contamination of a translucent object to be measured The following steps are provided: The beam is in the measurement object coupled, so that the beam is guided in the measured object. The beam is decoupled from the measured object and detected. A characteristic of the detected beam is given with a predetermined Reference value compared.

advantageously, the beam is at least once on one side of the measurement object reflected. The beam will depend on the contamination of the Side muffled.

advantageously, The radiation is amplitude modulated to reflect the influence of ambient light to reduce the measurement. In one embodiment, an intensity or a intensity change of the beam detected. The intensity of a ray is easier Way to detect, for example by a photodiode. A intensity change is advantageously detected when in the measurement result otherwise a uniform irradiation of the ambient light would flow.

In a further embodiment it is envisaged that a bandpass filtering will occur which is appropriate the spectrum of ambient light should be largely blanked out. This is advantageous if the beam has a narrow spectrum, which would be the case, for example, with a laser beam.

Further advantageous embodiments of the invention are in the subordinate claims specified.

following the invention with reference to the drawings based on embodiments explained.

It demonstrate:

1 an embodiment of a measuring system with a measuring device,

2 a diagram that illustrates the attenuation as contamination of the DUT increases.

1 schematically shows a cover for a lighting device. The cover is the measurement object 7 whose pollution is measured. In this embodiment, the measurement object is shown plan. It should be noted that in alternative embodiments (not shown), the first and second sides are not parallel to each other or the measurement object is not planar, but curved, for example.

The measurement object 7 has a first page 8th and a second page 9 , The cover is positioned such that the first side 8th the illumination device (not shown) is facing, so that in operation, the radiated light from the illumination source, the measurement object 7 goes through and from the second page 9 is emitted. The second page 9 is increasingly exposed to environmental influences and can consequently pollute.

On the first page 8th of the measurement object 7 is a measuring device 20 positioned. Positioning on the first side will reduce the impact of environmental factors on the measuring device 20 - in particular associated pollution - reduced.

The measuring device 20 comprises a radiation source, which in this embodiment as a light source 1 is formed, a coupling device 3 and a decoupling device 5 that on the first page 8th of the measurement object 7 are positioned, as well as a radiation detector, in this off guide example as a light detector 6 is formed, and a comparison device 10 ,

The light source 1 generates a ray of light 2 , Light is understood to be electromagnetic waves, in particular light in the visible range but also in the ultraviolet and infrared ranges. In one embodiment, the light source 1 a semiconductor device, for example, a device comprising a light-emitting diode (LED) or a laser, which has a narrow-band spectrum.

The coupling device 3 and the decoupling device 5 are with a transparent glue 4 on the first page 8th of the measurement object 7 fixed. In an alternative embodiment (not shown), the measurement object and the input and the output device are integrally formed. The input and the output device are in this case an integral part of the measurement object. This avoids refraction or damping effects at the transitions between input and output device and object to be measured.

In this embodiment, the coupling device 3 and the decoupling device 5 designed as a prism. The prisms are light-guiding elements made of transparent material. The prisms have a flat base in the shape of a right triangle. Other forms are conceivable.

The coupling device 3 has an entry page 31 and an exit side 32 that on the first page 8th of the measurement object 7 is positioned. The light source 1 is positioned so that its light beam 2 on the entry side 31 in the coupling device 3 entry. In one embodiment, the light source 1 adjacent to the entrance surface 31 positioned. In one embodiment, the light source touches 1 the coupling device 3 ,

The light beam 2 goes through the coupling device 3 , The light beam 2 will be at the exit surface 32 in such a way in the measurement object 7 coupled to him at least on one side 9 of the measurement object 7 is reflected.

In this embodiment, the light beam 2 in the coupling device 3 reflected on one side of the prism. In this embodiment, the light beam passes 2 initially parallel or nearly parallel to the first page 8th of the measurement object 7 and is reflected such that the light beam 2 at the decoupling surface 32 exit and into the test object 7 is entered.

The sides of the coupling device 3 , which reflect the light, are preferably mirrored to avoid damping effects. Advantageously, the coupling device 3 shielded from ambient light. This can be done, for example, with a cover 12 be achieved. Ambient light is light radiation into the measuring device 20 not from the light beam 2 is derived, including the light generated by the illumination device (not shown). The cover 12 is preferably formed and / or arranged such that the coupling device 3 and / or the decoupling device 5 apart from the side facing the measuring object is shielded from ambient light on all sides.

When coupling into the test object 7 becomes the light beam 2 at the interface between the coupling device 3 and measuring object 8th largely transmitted.

The light-guiding part of the coupling device 3 has a similar refractive index as the target 7 , Also, the refractive index of the adhesive 4 is advantageously similar. A similar refractive index leads to the fact that refraction and damping effects at the interface are largely avoided or reduced. By similar refractive index, a refractive index can be understood, so that the light beam 2 when crossing the coupling device 3 is not or only partially reflected into the measurement object.

The coupled light beam 2 will be on the first and the second page 8th . 9 of the measurement object 7 reflected several times so that it zigzags along the measurement object 7 running. Advantageously, the light beam 2 in such a way in the measurement object 7 coupled, so that the light beam on the sides 7 . 9 of the measurement object 8th is totally reflected.

The decoupling takes place by means of the decoupling device 5 with an entry area 51 and an exit surface 52 , The refractive index of the primate is chosen such that it does not reflect the light beam 2 comes, but to an at least substantial transmission of the light beam 2 in the decoupling device 5 , Advantageously, the light-guiding part of the decoupling device 5 , the glue 4 and the measurement object 7 a similar refractive index.

The light beam 2 runs in the decoupling device 5 such that it comes from a detector 6 can be detected at the exit surface 52 the decoupling device 5 is positioned. This can be done, for example, by the light beam 2 directly from the entrance area 51 over the exit surface 52 on the light detector 6 meets, as in 1 through the beam path 2a shown. But it is also conceivable that the light beam 2 is again reflected in the decoupling device, as in 1 by the beam path 2 B shown. For this purpose, the decoupling device 5 shaped like a prism, which allows the light beam 2 reflect in such a way that he is looking at the light detector 6 meets. Advantageously, the reflection side of the coupling-out device 5 mirrored to preserve the signal quality. The influence of ambient light can be through a cover 12 be reduced to shield. The cover for shielding the decoupling device 5 can with the cover to shield the coupling device 3 be connected or it may be provided a separate cover for shielding the decoupling device. The shielding can take place alternatively or additionally, in which an opaque layer, preferably above the mirror layer, is applied to the decoupling device. Such an opaque layer is alternatively or additionally optionally also for the shielding of the coupling device 3 suitable for ambient light. A shielding of the coupling device and / or the coupling-out device against ambient light is preferably provided on all sides except on the side facing the measuring object, the coupling-out device or the coupling device. In particular, a shield laterally adjacent to the coupling device 3 and / or the decoupling device 5 on the website 8th be provided of the measurement object.

The light detector 6 may be formed as a semiconductor device. An embodiment includes a photodiode which is suitable for the light intensity of the light beam 2 to detect. The light detector 6 generates a signal dependent on the detected light, for example a current or voltage value, of a downstream comparison device 10 provided.

A comparison device 10 compares the detected intensity of the light beam 2 with a given comparison value. Based on the result can be read, whether a cleaning of the DUT 7 is required or what degree of contamination it has.

In one embodiment, the comparator shows 10 whether a predetermined degree of contamination has been reached, for example by a signal tone or a signal light. In this case, the comparator compares 10 whether the the output signal of the light detector 6 is below or above the predetermined reference value.

Alternatively, the comparator 10 a value from which the degree of contamination can be read off. In one embodiment, this value is between 0 and 1, where 1 corresponds to an unpolluted object to be measured and 0 corresponds to contamination associated with opacity.

It should be noted that the comparison device can also be designed such that the result is transmitted to a display device, be it via contact means or contactless. Such a display device may be on the second side 9 be attached to the measuring object or beyond the lighting device or its cover.

The measurement of pollution is based on the fact that with increasing pollution the coupled light beam 2 is more attenuated. Due to the contamination of the test object 7 becomes the light when reflected on the second side 9 partially absorbed. This effect is more pronounced, the more often the light from the second side 9 of the measurement object 7 reflected and thus damped.

By the multiple reflection becomes the detection of the pollution degree facilitates and increases the accuracy of measurement. A little pollution, For example, by a few percentage points, would be at only one-time reflection to detect with a sensitive detector. By the multiple Reflection multiplied However, the damping effect, so that even a slight contamination is easier to detect.

The measurement becomes more accurate with multiple reflections. For example, the light beam 2 Reflecting on a spot where there is a partial heavy pollution or a partial weak pollution, the multiple reflection will reduce the influence of the partial heavy pollution or the partial weak pollution on the overall result. The multiple reflection causes an average measurement to be automatically taken over a larger area where the beam is reflected.

Based on the distance 11 between the coupling device 2 and the decoupling device 5 can be the number of reflections of the light beam 2 within the test object 7 vary. The greater the distance 11 is, the more reflections are made. The distance 11 For example, it can be between 1 cm and 10 cm.

The distance 11 can be selected depending on the degree of contamination to be detected. If low levels of contamination are to be detected, it may be advantageous to choose a larger distance in order to increase the number of reflections. This improves the dynamic range. If the detection concentrates more on heavy soiling, then a smaller distance can be an advantage, since heavy contamination leads to a significant attenuation of the light beam even with few reflections 2 lead, which can be detected.

2 illustrated by a diagram, the attenuation of the light beam at different levels of contamination and at different distances between the input and output device 3 . 5 ,

On the X-axis representatively different degrees of contamination of a glass pane are applied. 51 corresponds to clean glass. 52 corresponds to a low pollution. 53 corresponds to a medium pollution, and 54 corresponds to a high pollution.

A relative signal value is plotted on the Y axis. In this case, the received signal is set in relation to the signal that is detected on a non-contaminated disc, so that the value for the unpolluted object to be measured 1 is.

The curves 61 . 62 . 63 . 64 Each contains four values, which are displayed with markers. The curves represent different distances 11 between the input and output device 3 . 5 ,

Curve 61 is a transmission curve. That is, curve 61 indicates the extent to which the intensity of the transmitted light decreases due to increasing pollution. In this case there is a linear relationship between signal degradation and contamination.

Curve 62 shows the change of the relative signal at a small distance, in this example 2 cm, between the input and output device. It can be seen that the signal is more strongly degraded by the multiple reflection than is the case with the transmission. The curves 63 and 64 show the relative signal when the distance between input and output device is further increased. In the case of the curve 63 it is 4 cm, in the case of the curve 64 it is 6 cm. It can be seen that the relative signal is further degraded by the increased distance between the input and output coupling device, so that even with small soiling 52 a clear signal degradation is recognizable. This results in the highest damping for the largest distance selected in conjunction with the most heavily soiled disc. The relationship between the disc contamination and the measured values is clear. For larger distances between the input and output device results in a higher attenuation. The measurement can be used to derive a reliable statement about the contamination of the DUT.

A calibration of the comparison device 10 can be made, for example, by taking a measurement with a clean object to be measured and a measurement at a given degree of contamination, in which a cleaning is to take place. If this degree of contamination has been detected in a subsequent measurement, for example, a signal is emitted, which signals the pollution and required cleaning.

It It should be noted that measurement results determined largely unaffected by environmental parameters when no ambient light occurs. This is in a lighting device the case when this lighting device is turned off. This However, in lighting equipment in tunnels to a Influencing traffic safety.

In order to carry out measurements even in ambient light, in particular during the operation of lighting devices, in one exemplary embodiment the light source 1 suitable to generate an amplitude modulated light signal. One form of amplitude modulated signal is a light pulse. One form of amplitude modulated signal is a sequence of light pulses. One form of amplitude modulated signal is a periodic on-off-keyed light signal. The light detector 6 is suitable to detect a change in the characteristic to be detected, for example a change in intensity. It is not detected an absolute value, but the level difference of the detected signal. By detecting the change, the influence of a constant ambient light in the detection is ignored. Such a measurement of the change in the light intensity is also referred to as offset measurement. A small change in intensity with little level fluctuation indicates heavy pollution, while a high intensity change is associated with low pollution. The detected change is compared with a reference value. If the input signal comprises a pulse sequence or is a periodic on-off-keyed light signal, a plurality of intensity changes can be detected so that the values can be averaged, which increases the measurement accuracy.

alternative it is also possible the light source with a carrier frequency to operate. It will be a narrowband light signal, for example generated by a laser, which with a bandpass filter on Detector is filtered.

The Bandpass filter largely filters the broadband ambient light and limited the detection on a narrow bandpass range.

It It should be noted that the features of the described measuring device and the described measuring system and method arbitrarily with each other can be combined.

Claims (15)

Measuring device ( 20 ) for measuring the contamination of a translucent object to be measured ( 7 ), the measuring device ( 20 ) comprises: - a radiation source ( 1 ), - a coupling device ( 3 ) for coupling a beam ( 2 ) into the measuring object ( 7 ), so that the beam ( 2 ) in the test object ( 7 ), - a decoupling device ( 5 ) for decoupling the beam ( 2 ) from the measurement object ( 7 ), - a radiation detector ( 6 ), - a comparison device ( 10 ), which is formed, a characteristic value of the detected beam ( 2 ) with a reference value. Measuring device ( 20 ) according to claim 1, characterized in that the coupling device ( 3 ) coupled the beam such that the beam ( 2 ) in the test object ( 7 ) at least once on one side ( 9 ) of the test object ( 7 ) is reflected. Measuring device ( 20 ) according to claim 1 or 2, characterized in that the coupling device ( 3 ) and / or the decoupling device ( 5 ) comprises a prism. Measuring device ( 20 ) according to one of claims 1 to 3, characterized in that the coupling device ( 3 ) and / or the decoupling device ( 5 ) comprises a reflective coating. Measuring device ( 20 ) according to one of claims 1 to 4, characterized in that the coupling device ( 3 ) and / or the decoupling device ( 5 ) are shielded against the ingress of ambient light. Measuring device ( 20 ) according to one of claims 1 to 5, characterized in that the coupling device ( 3 ) and / or the decoupling device ( 5 ) comprises a light guiding element, wherein the refractive index of the element is similar to the refractive index of the measuring object ( 7 ). Measuring device ( 20 ) according to one of claims 1 to 6, characterized in that the radiation source ( 1 ) is adapted to provide amplitude modulated radiation. Measuring device ( 20 ) according to one of claims 1 to 7, characterized in that the radiation detector ( 6 ) comprises a bandpass filter. Measuring system with a measuring device ( 20 ) according to one of the preceding claims and a transparent measuring object ( 7 ), which is a first page ( 8th ) and a second page ( 9 ), wherein the coupling device ( 3 ) and the decoupling device ( 5 ) of the measuring device ( 20 ) on the same side or on different sides of the measurement object ( 7 ) are positioned. Measuring system according to claim 9, characterized in that the coupling device ( 3 ) and the decoupling device ( 5 ) are positioned such that the beam ( 2 ) is reflected several times. Measuring system according to claim 9 or 10, characterized in that the measuring object ( 7 ) is a cover of a lighting device. Method for measuring the contamination of a transparent measuring object ( 7 ) comprising: - coupling a beam ( 2 ) into the measuring object ( 7 ), so that the beam ( 2 ) in the test object ( 7 ), - decoupling the beam ( 2 ) from the measurement object ( 7 ), - detection of the beam ( 2 ), - comparing a characteristic value of the detected beam ( 2 ) with a predetermined reference value. Method according to claim 12, characterized in that the jet ( 2 ) in the test object ( 7 ) at least once on one side ( 9 ) of the test object ( 7 ) is reflected. Method according to claim 12 or 13, characterized that the radiation is amplitude modulated. Method according to one of claims 12 to 14, characterized that a bandpass filtering takes place.