How to maintain a clear viewing area for optical surveillance devices

Abstract

A method for maintaining clarity of a viewing area through a transparent element (10) of an optical monitoring device (100) includes forming a closed liquid film (50) on a surface of the transparent element (10) and coupling ultrasonic waves (64) into the transparent element (10), whereby the ultrasonic waves (64) coupled into the liquid film (50) and / or the transparent element (10) facilitate the dislodging of contaminants (70) and / or deposits on the transparent element (10).

Description

[Background technology]

[0001] Optical surveillance devices are, for example, cameras, radar devices, laser scanners, infrared cameras, etc. Since optical surveillance devices receive and, if necessary, emit electromagnetic waves in the visible and invisible wavelength ranges, it is important that the viewing area of ​​such optical surveillance devices is largely unobstructed in order to obtain the highest possible light yield and the least possible scattering effects.

[0002] Optical monitoring devices are therefore usually equipped with a protective screen that is optically transparent in the relevant wavelength range and that can be cleaned in various ways. This cleaning can be done manually or automatically by mechanical means, for example by windscreen wipers. Since mechanical means also impair the field of view at least temporarily, an alternative option is to clean the optical monitoring device by an ultrasonic device.

[0003] For example, EP 3618415 A1 discloses an optical monitoring device that includes a cleaning device that excites a dome-shaped cover plate with high-frequency sound, thereby moving a cleaning liquid from the edge area of ​​the cover plate to the center area. Any deposits on the cover glass are picked up by the liquid along its path and carried away with it. At the point of maximum energy in the ultrasonic field, the cleaning liquid evaporates, cleaning the cover glass.

[0004] Due to the fact that the cleaning liquid evaporates on the surface of the cover plate, solid residues may remain on the cover plate even if the liquid has completely evaporated.

[0005] The solid residues may be, for example, solid residues on the surface of the cover glass or components of the cleaning fluid that have been separated by the evaporation process. The solid residues are present at the point where the cleaning fluid has evaporated. This point may be within the viewing area, and in the worst case scenario, may be in the center of the viewing area of ​​the optical monitoring device. In particular, in environments that contain salt (road salt, sea spray), salt may accumulate on the cover glass.

[0006] Such residues shorten the operating cycle of such ultrasonic cleaning processes. Similarly, the cleaning fluid itself can impair visibility through the cover glass if it migrates to and accumulates at the energy maxima of the ultrasonic field.

[0007] These aforementioned disadvantages also occur in other prior art applications. German Patent Application Publication No. 2809748 describes a method for cleaning a surface by spraying a cleaning liquid onto the surface to be cleaned and then evaporating the sprayed liquid. This evaporation can also be achieved, for example, by using mechanical waves in the frequency range of 20 to 50 kHz. Again, the aforementioned residue problem occurs due to the evaporation of the cleaning liquid and the relatively small amount applied. Similarly, U.S. Patent Application Publication No. 2012 / 0243093 deals with the application of a fluid by, for example, a windshield wiper water system of an automobile and the subsequent evaporation of the fluid.

[0008] German Patent Application No. 4217559 also describes wetting the surface to be cleaned with a mist, which in practice is done intermittently.German Patent Application No. 102010041475 describes a vibration mechanism that vibrates the cover glass so as to remove the cleaning liquid sprayed on the cover glass from the cover glass.

[0009] German Patent Applications Nos. 102019123478, 102019130604, and 102019000306 describe automobile headlights whose surfaces can be excited by ultrasonic waves. The headlights are sprayed with liquid (covered in mist) by an ejector of a dispenser. Similarly, U.S. Patent Application Publication No. 2012 / 0117745 describes wetting a surface that is excited to vibrate by high-frequency sound using a spraying device. U.S. Patent Application Publication No. 2014 / 0299748 also shows that the combination of fluid application and ultrasonic waves causes the fluid to exit discrete outlets of a supply device and partially and intermittently wet the surface to be cleaned.

[0010] CN101885323 describes a method for using moisture present on the surface of a headlight to operate a headlight cleaning system. Summary of the Invention [Problem to be solved by the invention]

[0011] The object of the present invention is to provide a method by which the removal of foreign matter from the viewing area of ​​an optical monitoring device can be further improved, in particular by which solid deposits can be reliably removed.

[0012] For this purpose, a method is provided according to claim 1. Embodiments are obtained according to claims 2-14. [Means for solving the problem]

[0013] According to this method for maintaining clarity of the viewing area through a transparent element of an optical monitoring device, the following method steps are provided: forming a closed film of liquid on the surface of the transparent element; and coupling ultrasound waves into the transparent element, wherein the ultrasound waves coupled into the liquid film and / or the transparent element promote the detachment of contaminants and / or deposits on the transparent element.

[0014] It has been found that the presence of a liquid on the surface of a transparent element significantly reduces the energy required for ultrasound to separate the contaminants. The formation of a closed liquid film on the surface of the transparent element to be cleaned has the advantage that the optical characteristics of the field of view through the transparent element remain nearly constant. The transparent element to be cleaned may, for example, be the outer lens or protective window of an optical monitoring device. In particular, the refraction of light waves through the closed film is nearly identical. The frequency can be adjusted according to the type of contaminant to be removed, and the waveform for ultrasonic excitation can also be selected depending on the contaminant to be removed. The contaminant on the transparent element can be organic or inorganic. For example, insect residues, mineral deposits, oil films, growths, or metal residues may be mentioned in this context.

[0015] According to one embodiment of the present invention, the closed liquid film may be present on the entire surface of the transparent element or on a partial region of the transparent element. A closed liquid film is understood to mean continuous wetting of the transparent element with the liquid at least in a specific region. Thus, a continuous liquid layer is formed on the surface of the transparent element in at least some regions. Ultrasonic waves may be transmitted from the transparent element to the liquid film at least partially through the interface contact. By at least partially coupling the ultrasonic waves to the liquid, ultrasonic movement of the liquid or liquid film may be provided. The ultrasonic waves coupled to the transparent element, and optionally also to the liquid film, excite and vibrate the transparent element and any residues or contaminants present on the surface of the transparent element. The liquid surrounds the contaminants on the surface of the transparent element, thereby directing the ultrasonic waves coupled to the liquid to the contaminants or by vibration of the liquid itself, excites and vibrates the contaminants, or reduces adhesion to the transparent element.

[0016] According to one embodiment, the liquid may be provided by a tank internal or external to the optical monitoring device, or the liquid may be obtained from precipitation such as rain, dew or snow.

[0017] With appropriate energy input, the liquid can also be at least partially vaporized by ultrasound, which in a further embodiment can cause cavitation in the liquid, which further enhances the effect on contaminants or deposits on the surface of the transparent element, so that even strongly or firmly adhered contaminants can be detached or at least partially detached from the transparent element.

[0018] According to a more detailed embodiment of the method, the detached contaminants are transported out of the viewing area by the liquid. Using a liquid in addition to ultrasound is thus effective for removing contaminants and / or deposits from the transparent element. After the contaminants and / or deposits are detached, they can be transported out of the viewing area of ​​the optical monitoring device not only by ultrasound, but also, preferably, with the aid of a steady flow of liquid, or even entirely by such a flow of liquid. In this way, the energy from the ultrasound is preferably only needed for the secondary function of separating the contaminants and / or deposits and removing them after separation. Therefore, the energy requirements of the ultrasound can be metered in a controlled manner and reduced overall. For example, it may be possible to intermittently couple ultrasound to the transparent element and / or intermittently increase the energy input by the ultrasound for the separation or partial separation of the contaminants and / or deposits.

[0019] In an optional further embodiment of the method, it is provided that the ultrasonic waves propagate essentially within the outer layers of the transparent element. Alternatively or additionally, embodiments may provide that the ultrasonic waves are formed as surface waves. This has the advantage that in a multi-layer transparent element, such as a laminated glass window pane, the ultrasonic waves propagate only through layers where contamination and / or deposits may be present. This prevents ultrasonic energy from being emitted into the interior of the multi-layer transparent element that should not be cleaned, for example during layer modification by reflection or refraction.

[0020] According to one embodiment of the method, ultrasonic waves are coupled into the transparent element by at least one ultrasonic transducer. The ultrasonic transducer can be arranged on the surface of the transparent element to be cleaned or on its backside. In the case of a multi-layer transparent element, the ultrasonic transducer can be arranged on the layer to be cleaned. This can also include, in the case of a multi-layer element, arranging the ultrasonic transducer between the layer to be cleaned and another layer. According to a further development of the method, it is provided that at least one standing wave is formed between at least two ultrasonic transducers. The ultrasonic waves are advantageously coupled directly into the transparent element via the ultrasonic transducer, which is preferably arranged on the surface of the transparent element where the ultrasonic waves propagate, preferably as surface waves. In this way, losses due to impedance differences of intervening layers and / or elements are prevented. However, in the case of a single-layer transparent element, it is also possible to arrange the ultrasonic transducer on the backside of the surface where the ultrasonic waves propagate as surface waves. In the case of a multi-layer transparent element, the multi-layer structure allows the ultrasonic transducer to be arranged between two layers of the transparent element, and the ultrasonic waves can be preferably coupled directly into the layer where the ultrasonic waves propagate as surface waves. The formation of standing waves creates local energy maxima where the liquid and / or transparent element have the greatest amplitude, and in this region the mechanical effects on the contaminants and / or deposits and the liquid are greatest, so that the aforementioned effects occur preferentially in this region.

[0021] The ultrasonic transducer may be preferably designed to have one or more resonant frequencies. For this purpose, the ultrasonic transducer may have an electrode configuration that allows one or more resonant frequencies. In this way, the ultrasonic transducer can operate efficiently in several frequency ranges. This has the advantage of being able to separate different impurities and / or deposits.

[0022] According to a further embodiment of the method, the liquid may be supplied to the transparent element from the edge region. Supplying the liquid to the transparent element from the edge region has the advantage that the liquid can be spread evenly over the transparent element. The liquid may be provided as a component of water. According to an optional further embodiment, a cleaning agent may be provided as a component of the liquid. Water is readily available and does not have any special requirements for storage, distribution, or use, making it suitable as a component of the liquid, particularly the main component. It is advantageous to provide a cleaning agent as a further component of the liquid, since the cleaning agent can remove contaminants and / or deposits from the transparent element, particularly by chemical means, thereby reducing the need for ultrasonic energy input. Furthermore, with regard to ultrasonic cleaning, it may be advantageous that the cleaning agent can reduce the surface tension of water. This improves the bonding between the contaminants and / or deposits and the aqueous liquid.

[0023] Further embodiments of the method provide for the intermittent or permanent addition of a cleaning agent and / or disinfectant to the liquid. Furthermore, intermittent addition of gas to the liquid during supply may be provided. In this case, the advantages described above for cleaning agents occur, and this also applies equally to disinfectants. Intermittent mixing or addition of cleaning agents and / or disinfectants effectively represents the consumption of these additives as needed. In this way, maintenance intervals for replenishing the cleaning agent and / or disinfectant can be extended. For example, intermittent addition of gas, which may be compressed air, can displace deposits that cannot be removed by liquid and / or ultrasound.

[0024] The method is optionally embodied in that the liquid flows from the first side of the transparent member to the second side of the transparent member, forming a flowing overlayer on the surface of the transparent element. According to further embodiments, it may be provided that the flowing overlayer has a constant thickness or film thickness. According to certain embodiments, it may additionally be provided that the flow of the flowing overlayer is laminar and / or continuous. According to further embodiments, it may be provided that the fluid flow is at least partially driven by a gravity component. An advantage of providing a flow in the liquid is that contaminants and / or deposits separated by ultrasound or the liquid itself do not need to be carried out of the viewing area by ultrasound. This removal is advantageously achieved by the flow of the liquid rather than by ultrasound.

[0025] According to one embodiment of the method, it is provided that the liquid is supplied at a first side of the transparent element, and in further embodiments, it may be provided that the supply takes place through one or more outlets at the first side. The outlets may be formed as openings in the edge region of the recess into which the transparent element is inserted. Similarly, a single opening, particularly a trapezoidal opening, may be provided in the direction of the transparent window. In this way, uniform wetting of the surface of the transparent element is achieved, and the combined ultrasonic coupling improves the cleaning result. According to one embodiment, it is provided that the liquid is discharged at a second side of the transparent element, and in further embodiments, it may be discharged through one or more inlets at the second side. In a more detailed embodiment of the method, it is provided that the liquid is supplied to the supply line in a circuit. In further embodiments, liquid treatment may be performed in the circuit between the inlet and the outlet. In this way, the liquid, and in particular the optionally added cleaning agent and / or disinfectant, can be reused, thus saving process resources and designing correspondingly longer maintenance intervals.

[0026] According to a further embodiment of the method, it is provided that the control unit regulates the supply of liquid and / or generates a control signal for generating ultrasound waves. According to another embodiment, it is provided that the control unit regulates the addition of a cleaning agent and / or disinfectant to the liquid and / or controls an intermittent gas phase. Therefore, in a suitable further embodiment, it may be provided that the control unit automatically increases the flow of liquid for a short period of time. All of this contributes to a more efficient use of liquid and / or energy for ultrasound excitation. By providing a gas phase in the cleaning liquid, which can be provided, for example, by added compressed air, it is possible to mobilize contaminants that cannot be removed by the liquid and / or ultrasound waves. The same applies to the automatic, short-term increase in the flow of liquid.

[0027] According to another embodiment of the method, it is provided that the transparent element is temporarily wetted with a closed film of liquid. By temporarily, but in this case preferably completely, wetting the transparent element, consumption or use of the liquid can be further optimized. Therefore, in a preferred embodiment, the transparent element is wetted with a closed film of liquid only when cleaning of the transparent element is indicated. Thus, according to a further embodiment of the method, a device is provided for detecting contamination on the surface of the transparent element, and when contamination is detected, the transparent element is wetted with a closed film of liquid.

[0028] The invention will now be explained in more detail with reference to the embodiments shown in the drawings. [Brief explanation of the drawings]

[0029] [Figure 1] 1 is a schematic diagram of an optical monitoring device in which the method is implemented; [Figure 2] 1 is a schematic diagram of a cleaning process for a transparent element. DETAILED DESCRIPTION OF THE INVENTION

[0030] FIG. 1 shows an optical monitoring device 100 in which the method can be implemented. Optical means, such as a camera (not shown here for clarity), are arranged in a housing 110. The housing 110 includes a viewing window (not shown here) as a transparent element 10. The transparent element 10 is arranged in an edge region 130 of a recess 120. A liquid is supplied to this edge region 130 via a supply line 30 and directed to the surface of the transparent element 10 through an outlet 32 ​​in this edge region 130. The liquid forms a closed film 50 on the surface of the transparent element 10. At the edge region 130, the closed film 50 of liquid flows under gravity from the outlet 32, located on a first side 14 of the transparent element, to an inlet 42, located on a second side 16 of the transparent element 10 opposite the first side 14. Here, the liquid forms a flowing coating layer with a certain thickness. The inlet 42 opens into a discharge conduit 40 (not shown). The inlet conduit 30 and the outlet conduit 40 may be connected to each other in a circuit in which the fluid may be treated.

[0031] FIG. 2 shows a transparent element 10 with two ultrasonic transducers 60, 62 attached to the outer surface 12 of the transparent element 10. The transparent element 10 may be formed as a multilayer element, such as a laminated glass window pane. The ultrasonic transducers 60, 62 are in contact with the layer of the transparent element 10 to be cleaned. The ultrasonic transducers 60, 62 couple ultrasonic waves 64 into the transparent element. Thus, the ultrasonic transducers may be positioned on the surface of the transparent element 10 to be cleaned. In the case of a single-layer transparent element 10, it is also possible to position the ultrasonic transducers 60, 62 behind the surface through which the ultrasonic waves 64 propagate, preferably as surface waves. In the case of a multilayer transparent element 10, the multilayer structure allows the ultrasonic transducers 60, 62 to be positioned between two layers of the transparent element 10, allowing the ultrasonic waves 64 to be coupled, preferably directly, to the layer through which the ultrasonic waves 64 propagate as surface waves. The ultrasonic transducers 60, 62 are suitable for transmitting and receiving ultrasonic waves 64. By receiving the ultrasonic signals emitted by the ultrasonic transducers 60, 62 and analyzing the received ultrasonic signals, it is possible to determine whether or not contaminants 70 are present on the transparent element 10. In this way, it is possible to ensure that the cleaning process is carried out only if contaminants 70 are actually present on the transparent element 10.

[0032] A closed film 50 of liquid is formed on the surface of the transparent element 10 by the outlet 32 ​​described in Figure 1. Figure 2 shows a contaminant 70 to be dislodged or removed in a central region of the transparent element 10. However, the contaminant 70 may be located anywhere on the outer surface 12 of the transparent element 10. The closed film 50 of liquid surrounds the contaminant 70 on all sides and, in one embodiment, may flow over the contaminant 70.

[0033] The ultrasonic waves 64 emitted by the ultrasonic transducers 60, 62 are also coupled to the transparent element 10 and / or the liquid confined membrane 50 by the ultrasonic transducers 60, 62, causing both the transparent element 10 and the liquid confined membrane 50 to vibrate.

[0034] These vibrations result in the detachment of the contaminants 70 from the transparent element 10. The detachment of the contaminants 70 can be enhanced by increasing the energy input from the ultrasound 64. This results in partial evaporation 52 of the liquid and / or evaporation of the contaminants 70 themselves. Further increases in energy input may result in cavitation 54 within the liquid and / or contaminants 70, further aiding in the separation of the contaminants 70 from the transparent element.

[0035] In addition to increasing the energy input, it may also be provided to increase the flow of liquid at the surface of the transparent element 10. This improves the removal of the detached or at least partially detached impurities 70.

[0036] Similarly, a gas such as air may be intermittently blown out of outlets 32 along with the liquid, which may further aid in separating and / or removing contaminants 70 or may effectively remove residual liquid from transparent element 10. [Explanation of symbols]

[0037] 10 Transparent Elements 12 Exterior 14 First Aspect 16 The Second Aspect 30 Inlet conduit 32 Exit 40 Discharge conduit 42 Entrance 50 Closed Membrane 52 Evaporation 54 Cavitation 60, 62 Ultrasonic transducer 64 Ultrasound 70 Contaminants 100 Optical monitoring device 110 Case 120 recess 130 Edge area

Claims

1. A method for maintaining clarity of a viewing area through a transparent element (10) of an optical monitoring device (100), comprising: forming a closed film (50) of liquid on the surface of said transparent element (10); coupling ultrasound waves (64) into the transparent element (10), wherein the ultrasound waves (64) coupled into the liquid film (50) and / or the transparent element (10) facilitate the detachment of contaminants (70) and / or deposits from the transparent element (10); Including, The method wherein the liquid flows from the first side (14) of the transparent element to the second side (16) of the transparent element (10) to form a flowing top layer on the surface of the transparent element.

2. The method of claim 1, wherein the ultrasonic waves (64) are at least partially coupled to the liquid, and the liquid is moved by the ultrasonic waves (64).

3. 3. The method of claim 1 or 2, wherein the liquid is at least partially vaporized by the ultrasound (64).

4. The method according to any one of claims 1 to 3, wherein the ultrasonic waves (64) are coupled to the transparent element (10) via at least one ultrasonic transducer (60, 62).

5. The method according to any one of the preceding claims, wherein the liquid is supplied to the transparent element (10) from an edge region (130).

6. The method according to any one of claims 1 to 5, wherein a cleaning agent and / or a disinfecting agent is added to the liquid intermittently or permanently.

7. The method of any one of claims 1 to 6, wherein gas is added intermittently to the liquid while the liquid is being supplied.

8. The method according to any one of claims 1 to 7, wherein the flowing upper layer has a constant thickness.

9. 9. The method according to any one of claims 1 to 8, wherein the liquid is supplied at a first side (14) of the transparent element (10), the supplying being through one or more outlets (32) in the first side (14).

10. A method according to any one of the preceding claims, wherein the transparent element (10) is temporarily wetted with the closed film (50) of the liquid.

11. 11. The method according to any one of claims 1 to 10, wherein a device for detecting the contaminant (70) is provided on the surface of the transparent element (10), and when the contaminant (70) is detected, the transparent element (10) is wetted with the closed film (50) of the liquid.

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