EP1941248A1 - Detecteur de niveau de fluide optique - Google Patents
Detecteur de niveau de fluide optiqueInfo
- Publication number
- EP1941248A1 EP1941248A1 EP06794815A EP06794815A EP1941248A1 EP 1941248 A1 EP1941248 A1 EP 1941248A1 EP 06794815 A EP06794815 A EP 06794815A EP 06794815 A EP06794815 A EP 06794815A EP 1941248 A1 EP1941248 A1 EP 1941248A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- light
- liquid level
- level sensor
- detector
- optical
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- 239000012530 fluid Substances 0.000 title claims abstract description 66
- 230000003287 optical effect Effects 0.000 title claims abstract description 61
- 239000007788 liquid Substances 0.000 claims abstract description 27
- 230000005855 radiation Effects 0.000 claims abstract description 12
- 230000005499 meniscus Effects 0.000 claims abstract description 6
- 230000001419 dependent effect Effects 0.000 claims abstract description 5
- 238000004458 analytical method Methods 0.000 claims abstract description 4
- 230000007704 transition Effects 0.000 claims description 16
- 238000012545 processing Methods 0.000 claims description 6
- 238000000034 method Methods 0.000 claims description 3
- 230000008569 process Effects 0.000 claims description 3
- 239000000446 fuel Substances 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 230000008901 benefit Effects 0.000 description 4
- 239000011248 coating agent Substances 0.000 description 4
- 238000000576 coating method Methods 0.000 description 4
- 239000002828 fuel tank Substances 0.000 description 4
- 238000005259 measurement Methods 0.000 description 4
- 239000011521 glass Substances 0.000 description 3
- 238000003384 imaging method Methods 0.000 description 3
- 238000012544 monitoring process Methods 0.000 description 3
- 239000004033 plastic Substances 0.000 description 3
- 230000005540 biological transmission Effects 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000005286 illumination Methods 0.000 description 2
- 238000003491 array Methods 0.000 description 1
- 238000010420 art technique Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 230000009365 direct transmission Effects 0.000 description 1
- 230000006870 function Effects 0.000 description 1
- 239000002991 molded plastic Substances 0.000 description 1
- 239000010705 motor oil Substances 0.000 description 1
- 239000003921 oil Substances 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 238000004513 sizing Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
- G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
- G01F23/28—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring the variations of parameters of electromagnetic or acoustic waves applied directly to the liquid or fluent solid material
- G01F23/284—Electromagnetic waves
- G01F23/292—Light, e.g. infrared or ultraviolet
Definitions
- This invention relates to an optical fluid level detector. It in particular but not exclusively relates to a level detector capable of providing information about the level of fluid in a container. It is envisaged that the invention may be especially suited to detecting the level of fuel in a vehicle fuel tank, or perhaps the level of oil or brake fluid in a reservoir or sump.
- level sensor Many types of level sensor are known.
- One particular type employs a light source from which light is transmitted, a detector for detecting the transmitted light, and an optical element which defines an optical path along which the light from the source can be carried to the detector.
- the element includes at least one surface from which the light is reflected when in contact with air towards the detector. Similarly, when in contact with the liquid total internal reflection will not occur and the light passes through away from the detector. This face is located above the lowest level of the tank and below a level that the fluid will reach as the container is filled. The change from reflection to transmission will occur as the level in the container is varied, which in turn changes the intensity of light reaching the detector, and hence the voltage output from the detector. This intensity can therefore be used to provide information about the level of the fluid.
- two elements are provided which are spaced apart to define a gap which can be filled by the fluid as the level rises.
- the elements are arranged to guide light from one to the other across the gap and on to the detector when the fluid is present.
- total internal reflection again occurs sending light away from the detector.
- this changes the intensity of light reaching the detector to provide information on fluid level.
- an optical liquid level sensor comprising: a source of optical radiation; an optical detector sensitive to the optical radiation; and at least one optical element forming a surface which is positioned within a container and in which the light source directs radiation towards the surface to form a pattern which is dependent upon the level of the fluid; characterised in that the detector comprises an array of M detecting elements, where M is greater than 1, which elements capture an image of the pattern of radiation formed by the source upon the surface whereby the level of the fluid can be determined by analysing the image captured by the detector array.
- the surface may be a transmissive surface, by which we mean an interface through which at least some of the light from the source passes on its way to the detecting elements, or a reflective surface by which we mean a surface from which at least some of the light is reflected on its way to the detecting elements. It may be the external surface of the optical element, or an internal surface. The level of fluid will alter the pattern of light that passes through the surface or is reflected from the surface.
- the surface may be positioned within the container so that different portions become submerged as the fluid level rises.
- the level can be calculated without the need to calibrate for the intensity of the light source provided that the relative illumination of the overall surface is not varied. This provides a considerable and previously unforeseen benefit when compared with prior art systems that use a single photodetector and measure a single intensity value.
- the reflecting surface may comprise an external face of the optical element or it may comprise an internal face.
- the surface may be viewed directly by the detector such that it directly images the pattern.
- the pattern may itself be reflected in another surface before it is incident upon the detector.
- the detector may comprise a linear array of detector elements, by which we mean a row of detector elements. There may be any number of elements greater than one, but a most preferred arrangement could use at least 16, at least 32, preferably at least 64 and most preferably 128 elements .
- the detector array may be a two dimensional array.
- a lens may be provided between the surface on which the pattern is to be observed and the detector array.
- the lens may be positioned such as to focus an image of the pattern reflected from (or passing through) the reflective surface onto the detector array. This allows the array to "see” the pattern of light from the reflector.
- It may be a fresnel lens, which can conveniently be of plastic or glass material. It may be moulded to shape, which is convenient as it is low cost compared with a conventional ground lens. This is possible in this application since the quality of the image need not be that high.
- It may be a cylindrical or rod lens which focuses the light into a one- dimensional strip that is imaged by the detector array.
- the lens may be part of the optical element, e.g. it may be molded into a face of the optical element.
- An electronic processing means may be provided which is adapted to process the output from the detector elements of the detector array. It may be adapted to identify the position along the array at which the light incident. on the array changes from high intensity to a lower intensity. This will, depending on the design, correspond to the level at which the fluid reaches up the optical element.
- each element of the array may produce an output voltage or current having a magnitude that is a function of the intensity of light incident upon it.
- the processing means may determine the point along the array at which the voltage or current magnitude changes corresponding to the level of light.
- a number of measurements may be taken at different times and the average measurement of level taken. This may, for example, allow changes in level that occur when a container of fluid is moving to be compensated.
- An example of this is application to a vehicle fuel tank in which the fluid will slop around as the vehicle accelerates, decelerates or travels around corners .
- the number of samples used to form the average and/or the time between each sample may be varied. When used to measure the level of fluid in a fuel tank of a vehicle they may be varied according to the operating state of the vehicle. If the vehicle is stationary less samples and/or shorter time intervals between them may be used so that a quick reading is obtained. Alternatively, if the vehicle is in motion or accelerating or cornering more samples or a longer interval between samples could be used.
- the processing unit may select the time intervals/number of samples automatically in response to information about the vehicles state. It could take information from various sensors to do this, such as an ignition sensing wire, vehicle speedometer, ABS sensors, yaw sensors etc.
- a detailed analysis of the sharpness of transition from light to dark could be made.
- This transition may be blurred due to the meniscus that will form at the interface between the fluid and the surface on which the pattern is formed.
- Changes in the nature of this transition determined by analysing the output of the detector elements in the region of the transitioned may be used to determine the shape of the meniscus and/or its size and hence determine one or more properties of the fluid. This could therefore be used to determine the condition of the fluid, such as an engine oil by determining its viscosity. Protection is sought through this application for such condition monitoring.
- optical element Several different types may be used as follows. It is to be noted that in each case, a surface is provided on which a pattern of light can be imaged by the detector array and which gives information about the fluid level.
- the optical element may. comprise a diffuse reflecting surface imaged by the detector array.
- this could be a planar surface that is roughened and extends down into the fluid container with the detector imaging a strip along its length.
- the reflecting surface is an internal surface
- it may comprise an internal surface of an optical element arranged to provide total internal reflection of light from the source, onto the detector when in air yet to transmit light away from the detector out of the element when the surface is submerged in the fluid. This works best if the refractive index of the material is matched to that of the fluid, and if the angle of incidence of the light on the surface is chosen to allow total internal reflection when in air.
- an additional reflective surface may be provided between the light source and that surface.
- This additional surface may be oriented to reflect light evenly from the source onto the surface and may therefore be diffuse. It may be coated with a diffuse reflective coating or may, for example, be roughened.
- the optical element may therefore comprise a prism and the two reflecting surfaces may be provided by opposite faces of the prism.
- This may have a wedge shape having an upper face where the light source and detector array are positioned and comprising opposite planar reflecting faces that taper towards one another away from the upper face.
- the angle of the two faces should be chosen to reflect light emitted by the source from one face to the other and then back to the source. When the wedge is submerged the total internal reflection will cease and light will transmit out of the wedge.
- the optical element may comprise a conical element which narrows in diameter towards the end furthest from the source/detector array may be provided.
- the reflecting surface will be made up of pairs of locations on the surface which are located diametrically opposite the axis of revolution of the conical element.
- optical elements there may be two optical elements, each having an optically transmissive face spaced from a corresponding optically transmissive face on the other to define a gap which may contain the fluid.
- the light may be adapted to pass through the gap when the faces are index matched by fluid in the gap, but otherwise be prevented from passing through by total internal reflection.
- two elements may each comprise a wedge shaped element.
- the reflecting surface, or another surface which either reflects or transmits light in the path from light source to detector array may have a stepped profile.
- Figure l(a) is a plan view of a first embodiment of a liquid level detector in accordance with a first aspect of the invention
- Figure l(b) is a graph showing the output of the detector elements of the embodiment of Figure l(a) at a first, low, level of fluid;
- Figure l(c) is a graph showing the output of the detector elements of the embodiment of Figure 1 at a second, higher, level of fluid;
- Figure 2 is a plan view of a second embodiment of a liquid level detector in accordance with a first aspect of the invention
- Figure 3 is a plan view of a third embodiment of a liquid level detector in accordance with a first aspect of the invention.
- Figure 4 is of a fourth embodiment of a liquid level detector in accordance with a first aspect of the invention.
- Figures 5 (a) and 5(b) illustrate the pattern of light imaged on the detector array for (a) sharp focusing optics and a very viscous fluid and (b) either lower quality focusing optics or a more viscous fluid.
- an optical level detector comprises of two optical elements 110, 120, each of which comprises a transparent prism of plastic or glass, that are positioned adjacent one another and extend downwards from an upper surface of a fluid container 130 such as a vehicle fuel tank.
- a sloping side 113,123 (by which we mean non-vertical) of each prism opposing the vertically aligned faces 112,122 extends downwardly at a non-vertical orientation such that the top of each prism is wider than the base.
- the sloping side 113,123 of one of the prisms is coated with a layer of diffuse material which, as will become apparent, makes the surface reflect diffusely.
- a light source 150 such as a light emitting diode, is positioned above a top face of the one of the prisms 119.
- the source emits light which may be visible or infra-red, and which is guided into the prism 110 through a diffuser (not shown) in such a way that the light is substantially uniform in its illumination of the sloping face of the prism 110. This light is then reflected from the sloping face onto the vertical face on the other side of the prism 110.
- the other prism 120 is provided with a reflective coating on its sloping face 122 which provides specular reflection. It may, for example, be silvered to provide a mirrored surface.
- a detector array 160 is located above this prism 120 which receives light reflected from the mirrored surface. This will correspond to light that has passed across the gap from the first prism 110.
- a fresnel lens (not shown) of moulded plastic is provided between the detector array 160 and the second prism 120 to guide any light that exists the prism onto the detector array such that the detector sees an image of the light reflected from the mirrored surface.
- the array will capture an image along its length of a corresponding linear strip of the entire mirrored surface.
- the lens may focus the surface of the reflector onto the array, but it could work without it being in focus.
- a cylindrical or rod lens could be used to focus the whole of the surface down into a thin strip that is imaged by the detector array. This has the advantage that light from the whole surface is focused onto the array.
- the detector array 160 is a one dimensional array of detecting elements or pixels. That is that the array is a group of pixels arranged on next to the other in a line. In a preferred arrangement the array consists of 128 detection pixels and associated read-out circuitry. Other arrays could of course be used. They may have more or less pixels, and they may be two dimensional rather than all arranged in a line. A grid of pixels could be provided.
- An electronic unit drives the light source and receives the output from each of the detector elements of the detector array.
- An image is captured by reading out all of the values of the pixels at a given time and storing the values in an electronic memory (not shown) .
- This electronic unit then processes the images seen by the array to determine the level of the fluid.
- fluid in the tank such as petrol or diesel will enter the space 140 between the two prisms 110,120. It will fill the space up to a level dependent upon the level of the fluid in the container, with air occupying any remaining unfilled space. Above the level of the fuel, light will be transmitted poorly across the space 140 between the two prisms 110,120 because the refractive index of plastic or glass differs greatly from that of air. The output from those detector elements of the array that are imaging the corresponding region of the mirrored surface will therefore be low. On the other hand, below the level of the fluid the amount of light transmitted will be greater as the fuel acts to index match the two facing surfaces of the prisms 110,120 . The output of the detector elements imaging the part of the mirrored surface corresponding to regions below the surface will therefore be higher.
- the image seen by the one-dimensional array for different fuel levels can be seen in Figures l(a) and l(b) .
- the image corresponds to the pattern of light that is seen on the sloping surface of the prism 120, which in turn depends on the pattern of light seen to pass across the space 140.
- the one dimensional image is analysed to determine the centre of the region where the image shows a transition from dark to light.
- Figure l(b) shows the pattern of light imaged by the detector at a low fluid level
- Figure l(c) shows the corresponding pattern of light at a higher level.
- This apparatus has an advantage over a prior art technique of simply looking at the overall intensity of light that is incident upon a single detector. There is, for example, no need to calibrate the intensity of the output of the LED. Also, any errors due to dirt on the reflectors or damage to the reflectors can be identified and taken into consideration.
- the image may or may not include a sharp transition from light to dark which indicates the level. Instead it may see a gradual transition. This will be the case if the reflector of the other prism is not completely specular or if the focusing of the lens is imperfect.
- FIG. 2 An alternative arrangement is shown in Figure 2 .
- This device again has two optical elements 210, 220 which each comprise a prism. As with the embodiment of Figure 1, they are again positioned one next to the other such that a gap 240 is formed between two facing surfaces of the prisms.
- both prisms define a surface which extends downwardly and inwardly so that the gap 240 narrows from top to bottom.
- the facing surface of the one prism 210 is coated with a diffuse reflecting surface.
- a light source 240 illuminates this surface from above, and the diffuse surface reflects light uniformly across the gap 230 towards the other facing surface of the other prism. This surface is mirrored with either a diffuse or specular reflective surface.
- a receiver 250 is located above the second surface to capture an image of the pattern of light reflected from the second surface.
- the prisms When the prisms are partially immersed in fluid, only the portion above the fluid level will reflect light from the source 240 on to the receiver 250. Below the surface, the light will be scattered from the fluid surface and a very small amount reach the receiver.
- Both the first and second prisms of this example may be separate elements as shown in the accompanying figures or may comprise parts of a single optical element.
- the gap and the two facing surfaces may be formed by an open ended hole which extends through the centre of a block of material.
- an optical element which comprises a substantially conical rod 310 which tapers in diameter from an upper end 311 towards it base 312.
- the base 312 of the rod is immersed in the fluid, with the fluid level rising up the outside of the rod as the tank is filled.
- the rod 310 may, as shown in the enlarged view of the rod, have faceted sides, by which we mean that rather than smoothly tapering from a first diameter at the upper end to a second, smaller diameter, at the lower end, its diameter changes in a series of steps.
- Each step is defined by an angled region of outer wall interconnecting a region which is angled by a lesser amount away from the vertical.
- a light source 320 such as an LED transmits light down into the rod 310 and a detector 330 array is positioned so that it collects light from the rod to form an image of the light reflected back from the rod.
- a screen 340 prevents direct transmission of light from the source 320 to the detector 330.
- each step provides regions at which light is reflected from one side of the rod to the other and back up to the receiver. In the absence of fluid, each step reflects and appears as a bright band on the receiver array separated by a dark band. When fluid is surrounding the rod 310, it index matches to the rod material and so the light will escape from the submerged step rather than reflecting internally.
- This embodiment is similar in operation to that of Figure 2, but rather than two prisms defining two prism surfaces a single prism 410 that has a reflecting surface 411 is provided which is inclined away from the vertical. This is provided with a diffuse coating and illuminated by a light source 420. A detector array 430 captures an image of the pattern of light reflected from the surface 411. A baffle 440 prevents light from the source directly illuminating the receiver.
- the light On the portion of the surface 411 that is above the level of the fluid, the light will be reflected to the receiver array 430 and appear as a bright region. On the portion below the surface, the light will be diffused and scattered by the fluid and so only a small amount will reach the detector. This will be apparent as a darker region. The transition from lighter to darker region in the image captured by the detector array will provide a measure of the level of the fluid on the surface.
- the prism element does not need to be transparent.
- the reflecting surface could be provided by a surface of the container itself for example, perhaps coated with a specular coating or simply roughened.
- the level of fluid is determined by analysing the pattern of light on the surface. This is performed by monitoring the output of the elements in a multi-element detector array. This provides more information than can be obtained by taking a single measurement of the overall amount of light reflected.
Landscapes
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Thermal Sciences (AREA)
- Fluid Mechanics (AREA)
- General Physics & Mathematics (AREA)
- Measurement Of Levels Of Liquids Or Fluent Solid Materials (AREA)
Abstract
La présente invention concerne un capteur de niveau de liquide optique qui comprend une source de rayonnement optique, un capteur optique sensible au rayonnement optique, et au moins un élément optique formant une surface qui est positionné à l'intérieur d'un boîtier et dans lequel la source lumineuse dirige le rayonnement vers la surface afin de former un motif qui dépend du niveau du fluide, le détecteur comprenant une matrice d'éléments de détection M, où M est supérieur à 1, lesquels éléments capturent une image du motif de rayonnement formé par la source sur la surface, le niveau du fluide pouvant ainsi être déterminé en analysant l'image capturée par la matrice de détecteur. Le dispositif est en mesure d'analyser à partir du motif un quelconque ménisque formé entre la surface et le sol et détermine à partir de cela la condition du fluide.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB0521800A GB0521800D0 (en) | 2005-10-26 | 2005-10-26 | Optical fluid level detector |
PCT/GB2006/003874 WO2007049005A1 (fr) | 2005-10-26 | 2006-10-19 | Detecteur de niveau de fluide optique |
Publications (1)
Publication Number | Publication Date |
---|---|
EP1941248A1 true EP1941248A1 (fr) | 2008-07-09 |
Family
ID=35515727
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP06794815A Withdrawn EP1941248A1 (fr) | 2005-10-26 | 2006-10-19 | Detecteur de niveau de fluide optique |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP1941248A1 (fr) |
GB (1) | GB0521800D0 (fr) |
WO (1) | WO2007049005A1 (fr) |
Families Citing this family (11)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
IL187597A0 (en) * | 2007-11-22 | 2008-03-20 | Dekel Tzidon | Fluid level indicator |
GB2520721A (en) * | 2013-11-29 | 2015-06-03 | Airbus Operations Ltd | Fuel surface height measurement |
US10326980B2 (en) | 2016-02-04 | 2019-06-18 | Simmonds Precision Products, Inc. | Imaging system for fuel tank analysis |
US9978137B2 (en) | 2016-02-04 | 2018-05-22 | Simmonds Precision Products, Inc. | Imaging system for fuel tank analysis |
US10041879B2 (en) | 2016-02-04 | 2018-08-07 | Simmonds Prevision Products, Inc. | Imaging system for fuel tank analysis |
US9921150B2 (en) | 2016-02-04 | 2018-03-20 | Simmonds Precision Products, Inc. | Imaging system for fuel tank analysis |
US10424076B2 (en) | 2016-02-04 | 2019-09-24 | Simmonds Precision Products, Inc. | Imaging system for fuel tank analysis |
US11069929B1 (en) | 2016-05-24 | 2021-07-20 | NDSL, Inc. | Apparatuses and methods for optically monitoring fluid level in a container, such as a battery, using a non-contact optical detector on an outside surface of the container |
US20200158555A1 (en) * | 2018-11-15 | 2020-05-21 | Hizero Technoogies Co., Ltd. | Liquid level detection system and liquid level detection method |
DE102019208563A1 (de) * | 2019-06-12 | 2020-12-17 | Volkswagen Aktiengesellschaft | Optischer Flüssigkeitssensor und Verfahren zur optischen Detektion von Flüssigkeiten |
DE102020214028A1 (de) | 2020-10-29 | 2022-05-05 | Continental Teves Ag & Co. Ohg | Optische Füllstandmessvorrichtung für einen Flüssigkeitsbehälter |
Family Cites Families (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB1603389A (en) * | 1978-05-31 | 1981-11-25 | Eaton S | Liquid level detector |
GB2149112B (en) * | 1983-10-27 | 1987-12-09 | Lucas Ind Plc | Liquid level detector |
US4873863A (en) * | 1988-11-29 | 1989-10-17 | Bruhl J D | Volumetric leak detection means and method |
GB9813429D0 (en) * | 1998-06-22 | 1998-08-19 | Cambridge Consultants | Apparatus and method for detecting the level of a liquid |
US6782122B1 (en) * | 2000-04-27 | 2004-08-24 | Simmonds Precision Products, Inc. | Apparatus for measuring height of a liquid in a container using area image pattern recognition techniques |
DE10206824B4 (de) * | 2002-02-18 | 2005-04-28 | Kautex Textron Gmbh & Co Kg | Verfahren zur optischen Füllstandsbestimmung in flüssigkeitsgefüllten Behältern |
-
2005
- 2005-10-26 GB GB0521800A patent/GB0521800D0/en not_active Ceased
-
2006
- 2006-10-19 WO PCT/GB2006/003874 patent/WO2007049005A1/fr active Application Filing
- 2006-10-19 EP EP06794815A patent/EP1941248A1/fr not_active Withdrawn
Non-Patent Citations (1)
Title |
---|
See references of WO2007049005A1 * |
Also Published As
Publication number | Publication date |
---|---|
GB0521800D0 (en) | 2005-12-07 |
WO2007049005A1 (fr) | 2007-05-03 |
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